Citation
Geological Survey professional papers

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Title:
Geological Survey professional papers
Abbreviated Title:
Geol. Surv. prof. pap.
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Geological Survey (U.S.)
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Washington, D.C.
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Edition:
NO. 306 A
Physical Description:
1083 v. : ill., maps ; 29 cm.

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Geology -- United States ( lcsh )
Aardwetenschappen ( gtt )
Geologie ( gtt )
Geology ( fast )
United States ( fast )
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serial ( sobekcm )
federal government publication ( marcgt )

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Citation/Reference:
Chemical abstracts
Dates or Sequential Designation:
216-1298.
General Note:
Cataloged separately in LC after no. 688.
General Note:
Monthly Catalog Number: gp 81009497
General Note:
Most titles sold on an individual basis by the Supt. of Docs., U.S. G.P.O.

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University of Florida
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Centers of Excellence at UF
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This item is a work of the U.S. federal government and not subject to copyright pursuant to 17 U.S.C. §105.
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023671617 ( ALEPH )
01445516 ( OCLC )
gs 14000289 ( LCCN )
0096-0446 ( ISSN )
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QE75 .P9 ( lcc )
551 ( ddc )
I 19.16: ( sudocs )

Related Items

Preceded by:
Professional paper (Geological Survey (U.S.))
Succeeded by:
U.S. Geological Survey professional paper

Aggregation Information

DLOC1:
Digital Library of the Caribbean
PCM:
Panama and the Canal
IUF:
University of Florida
IUFGOV:
Centers of Excellence at UF
UFPANCAN:
Documents of the Panama Canal

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Full Text
1 -


Geology and Paleontology Of Canal Z-one and Adjoining Parts of Panama

GEOLOGY AND DESCRIPTION OF TERTIARY MOLLUSKS (GASTROPODS: TROCHIDAE TO TURRITELLIDAE) GEOLOGICAL SURVEY PROFESSIONAL PAPER 306-A






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i 4









Geology and Paleontology Of Canal Lone and Adjoining Parts of Panama

GEOLOGY AND DESCRIPTION OF TERTIARY MOLLUSKS (GASTROPODS: TROCHIDAE TO TURRITELLIDAE) By W. P. WOODRING



GEOLOGICAL SURVEY PROFESSIONAL PAPER 306-A


A contribution to the history of the Panama land bridge


Or


UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON :1957























UNITED STATES DEPARTMENT OF THE INTERIOR

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY

Thomas B. Nolan, Director












o 199


For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C.
















CONTENTS


-bstract --_ __- -- _- _- -_-_Introduction _-____ ------------Historical background -- -- -
Purpose and scope of report
Orthography of geographic names
Acknowledgments _-_ ---..Annotated bibliography G eology ------ -_-_-_-_ --_-_-_---_-_Stratigraphy -- - - - --_-_-_Outline of stratigraphy
Cretaceous(?) system Eocene series --- --_Gatuncillo formation
Eocene or Oligocene series
Marine member of Bohio(?) formation -O ligocene series -- ..-_--- _--_---_ --__ -__ ----.
Bohio formation -_-- ----_-- _Caimito formation, exclusive of Madden
basin and Pacific coastal area _-.--..-.Tuffaceous strata in Chorrera area_-------Bas Obispo formation and Las Cascadas
agglom erate_ .. .... .... ...-_-- __- _..
Oligocene and Miocene series -- -----..
Caimito formation of Madden basin and
Pacific coastal area --- ._.._---- _-_----Miocene series.-......-_-..-...---.....
Culebra formation, including Emperador
lim estone m ember --- ...-...._.. ---. ..
Cucaracha formation _---- ____---- ___.-_PanamA formation, including La Boca
marine member and Pedro Miguel agglomerate member --- .--- -- _-- __-....
G atun form ation ___--._-_--.._ -_ -__.. -_Pliocene series ..-_ -- --- ..-_-----Chagres sandstone, including Toro limestone m em ber-.-.. -.. --.-_ ---_ ___-._Pleistocene series___- .-- ___-- _- .- ...-------.
Correlation of Tertiary formations in different


Page
1
2 2 3
4 4 5
10 10 10 13
13 13
22 22 24 24

28 31

31 32

32
34

34 39


39
42 47

47 50

50


Geology-Continued
Igneous rocks --__ --__--_ ---Cretaceous(?) volcanic and intrusive rocks.
Tertiary volcanic and intrusive rocks --Granular intrusive rocks
Dike rocks _--- -------Volcanic rocks and tuf
Chemical composition -A g e - -_ -_ - --_-_-_ --_-.- -_Structure _-_-- -- _--
Structural history Structural features ___
Mineral resources ---- ..-_ --_Metallic mineral deposits
Nonmetallic mineral deposits
Oil possibilities --_-_- -------Description of Tertiary mollusks
Gastropods -- .Family Trochidae _-_ - Family Turbinidae
Family Phasianellidae
Family Phasianellidae?
Family Neritidae
Family Thiaridae?
Family Littorinidae Family Vitrinellidae
Family Rissoidae
Family Rissoinidae
Family Xenophoridae Family Hipponicidae Family Hipponicidae?
Family Crepidulidae
Family Calyptraeidae
Family Naticidae
Family Turritellidae
Localities at which fossils were collected References cited ___Index- ------


Page

52 52 53 53
54 54 55 56
57 57 58 58 58 59 60
62 62 62
64 65 66
66 68 68 69
76 77
---- 77
78 78 79
79
84 97
---- 112
131 137


ILLUSTRATIONS


[Plates 1, 2 in pocket, plates 3-23 follow p. 145]

PLATE 1. Geologic map of Canal Zone and adjoining parts of Panam -----------In I
2. Geologic map of Gaillard Cut area, Canal Zone -__-_-_-_-_-.. --_-_--- --------------- In
3. Foraminiferal limestone from Gatuncillo formation of Madden basin, Panami.
4. Echinoid-bearing limestone from Gatuncillo formation of Madden basin, Panam.
5. Boulder conglomerate of Bohio formation at Salud Point, Barro Colorado Island, Canal Zone.
6. Poorly sorted conglomerate of Bohio formation on Transisthmian Highway near Las Cumbres, just south of
continental divide, Panamd.
7. Alhajuela sandstone member of Caimito formation at north abutment of Madden Dam, Canal Zone.
III


pocket ocket


-____ ___


areas.







IV CONTENTS

PLATE S. Emperador limestone member of Culebra formation on west bank of Panama Canal at canal station 1619, Canal
Zone.
9. Coralliferous limestone at base of La Boca marine member of Panamd formation on Rio Masambi 200 meters upstream from east bank of Panama Canal, Canal Zone.
10. Strata in middle part of Gatun formation on east side of Gatun Third Locks excavation, Canal Zone.
11. Toro limestone member of Chagres sandstone resting on marly siltstone in middle part of Gatun formation in
road cut 3 kilometers southwest of Gatun, Canal Zone.
12. Toro limestone member of Chagres sandstone in road cut 3 kilometers north-northwest of Gatun, Canal Zone.
13. Chagres sandstone in road cut 3 kilometers south of Lagarto, Panamd.
14. Middle and late Eocene mollusks from Gatuncillo formation.
15. Late Eocene or early Oligocene mollusks from marine member of Bohio(?) formation and late Oligocene mollusks
from middle member of Caimito formation in Gatun Lake area.
16. Early Miocene mollusks from Culebra formation and La Boca marine member of Panams formation.
17. Middle and late Miocene mollusks from Gatun formation.
18. Middle and late Miocene mollusks from Gatun formation and early Pliocene mollusk from Chagres sandstone.
19, 20. Middle Miocene mollusks from Gatun formation.
21, 22. Middle and late Miocene mollusks from Gatun formation.
23. Middle Miocene mollusks from Gatun formation.
Page
FIGURE 1. Map of Panamd showing principal areas of Tertiary marine sedimentary formations and area covered by plate I_ 11 2. Ungulate metapodial from transition zone between Culebra and Cucaracha formations -_------- 38 3. Reconnaissance geologic map of Caribbean coastal part of PanamA immediately west of Canal Zone ----_---__ 45 4. Correlation of Tertiary formations in different areas ----.. ----------- ------ ------------ 51











GEOLOGY AND PALEONTOLOGY OF CANAL ZONE AND ADJOINING PARTS OF PANAMA


GEOLOGY, AND DESCRIPTION OF TERTIARY MOLLUSKS (GASTROPODS: TROCHIDAE TO TURRITELLIDAE) By W. P. WOODRING ABSTRACT


Most of the area covered by the present report lies in the central Panamd area of Tertiary marine sedimentary rocks, which extends obliquely across the trend of the isthmus. The central Panamd area contains a sequence of Tertiary deposits, for the most part marine, ranging in age from middle Eocene to early Pliocene. In the southwestern part of the Canal Zone and farther west a thick sequence of volcanic rocks borders the marine area. In the Gaillard Cut area, along the Panama Canal, the marine and volcanic rocks interfinger.
The oldest rocks, forming the basement on which the Tertiary formations rest, are more or less altered basaltic and andesitic lavas. Altered tuffs containing microscopic marine fossils are interbedded with the lavas. These basement rocks are of Cretaceous(?) age. Sometime during Late Cretaceous, Paleocene, or early Eocene time they were strongly deformed and perhaps at about the same time were intruded by dioritic and dacitic rocks. This is the strongest regional deformation in the known geologic history of this part of Panamd.
The middle and upper Eocene Gatuncillo formation rests with marked unconformity on the basement rocks. The Gatuncillo is widely transgressive and is essentially uniform lithologically, consisting principally of fine-grained detrital rocks. There is no indication of nearby volcanism during middle and late Eocene time.
Volcanism reached a climax during Oligocene and early Miocene time. The volcanic centers, which presumably are now concealed by later volcanic rocks, evidently were located in southern Panamd not far west of the Canal Zone. A tongue of Oligocene(?) volcanic rocks, interpreted to have accumulated at the periphery of a volcanic pile, extends eastward across the canal in the northern part of the Gaillard Cut area. These volcanic rocks, consisting of agglomerate, tuff, and thin andesitic flows and flow breccias, constitute the Bas Obispo formation and Las Cascadas agglomerate. They are considered of Oligocene(?) age because of their inferred relation to Oligocene deposits in the adjoining marine area.
The Oligocene deposits in the marine area are heterogenous and contain much volcanic debris. The earliest of these deposits are basaltic boulder conglomerate and basaltic graywacke forming the Bohio formation. This coarse debris, directly overlying the fine-grained rocks of the Gatuncillo formation, indicates movements in the source areas. As a result of these movements the Bohio formation overlaps the Gatuncillo formation in the Pacific coastal area east of the Canal Zone. The Bas Obispo formation is thought to grade northward into the Bohio. Though the Bohio represents for the most part an extension of nonmarine deposits into the marine area, it includes marine deposits. Marine upper Eocene or lower Oligocene strata in the western part of the Gatun Lake area are interpreted as a marine member in the lower part of the Bohio(?); the basal part of the Bohio in the Quebrancha syncline includes lower Oligocene marine siltstone; and the upper part of the formation on Barro Colorado Island and in the Pacific coastal area contains thin upper Oligocene marine deposits.


Late Oligocene time also witnessed the deposition in the marine area of heterogenous strata overlying the Bohio formation. These strata are almost entirely marine and are grouped as the Caimito formation. The Caimito overlaps the Bohio in the northern part of Madden basin and apparently also northeast of Gatun Lake, where it evidently rests directly.on the basement. The overlap indicates continuation of the minor movements that affected the distribution of the Bohio formation. The Caimito formation is made up chiefly of tuffaceous sandstone, tuffaceous siltstone, conglomerate, tuff, agglomerate, and limestone. In the Quebrancha syncline it includes the economically important Quebrancha limestone member, which is quarried for the manufacture of cement. The lower member in the Gatun Lake area (or perhaps the entire formation) is thought to grade southward into the Las Cascadas agglomerate of the Gaillard Cut area.
Alternating marine and volcanic deposits were laid down in the Gaillard Cut area in early Miocene time. These deposits make up, in ascending order, the Culebra formation, including the Emperador limestone member, the Cucaracha formation, and the Panamd formation, including the La Boca marine member and the Pedro Miguel agglomerate member. Though the Culebra formation contains much tuffaceous material, it consists of dark thin-bedded shale, mudstone, and siltstone; calcareous sandstone, and limestone-all laid down during a minor marine transgression. The Cucaracha formation consists almost entirely of nonmarine tuff, altered to bentonitic clay. Tuff and relatively fine grained agglomerate are the chief constituents of the Panamd formation proper; silty mudstone, sandstone, limestone, and tuff make up the La Boca marine member; coarse-grained agglomerate the Pedro Miguel agglomerate member. The La Boca marine member represents a reinvasion of the sea that transgressed across the Cucaracha and Culebra formations onto the Bas Obispo formation. Two of these lower Miocene formations, the Culebra and Cucaracha, are readily eroded. They form topographic basins between hills of agglomerate and basalt, and these topographic basins determined the course of the canal. The Panamd formation is the youngest Tertiary formation in the Gaillard Cut area and in the Pacific coastal area east of the Canal Zone.
Tuffaceous sandstone and limestone deposited in Madden basin during early Miocene time are grouped with the underlying strata of late Oligocene age in that area as the Caimito formation. Though the lower Miocene part of the Caimito formation of Madden basin is thought to include the equivalent of the lower Miocene formations of the Gaillard Cut area, there is no satisfactory faunal or lithologic correlation from one area to the other. The lower Miocene formations of the Gaillard Cut area and the deposits in Madden basin considered to be their equivalent represent the early half of the early Miocene, which corresponds to the late Oligocene of some paleontologists. The youngest deposits in Madden basin (the Alhajuela sandstone member of the Caimito formation), however, are younger than the disputed Oligocene or Miocene. Madden basin is the only area where
1







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


late lower Miocene marine deposits have been found. They are almost exactly in the center of the present isthmus.
The Oligocene and lower Miocene volcanic rocks include widespread remnants of basalt flows in the Gaillard Cut and adjoining areas. The climax of volcanism during Oligocene and early Miocene time was accompanied by marked intrusive activity. Stocks of quartz diorite, diorite, and dacitic and andesitic rocks, dikes of andesite, and dikes and irregular bodies of basalt represent that interval of intrusive activity and are not known to be younger.
The Gatun formation was deposited during a middle and late Miocene marine transgression. The Gatun of the area covered by plate 1 is assigned to the middle Miocene. The upper part at the west end of the outcrop area is considered late Miocene. The relations between the Gatun formation and the Caimito formation-the next older formation in the Gatun Lake and Caribbean coastal areas-are unknown. The apparent absence of lower Miocene deposits in those areas indicates discontinuity, and transgressive overlap of the Caimito is shown by relations at the east end of the outcrop area of the Gatun, where it directly overlies the basement rocks. At least minor movements (and perhaps regional deformation) took place before the Gatun was deposited. How far inland beyond its present outcrop area the Gatun formation extended is not known. If it extended far inland, presumably it extended through Madden basin. The only tuff in the Gatun formation is very fine-grained and evidently was derived from a distant source.
The Chagres sandstone, including the Toro limestone member, represents a minor early Pliocene transgression. The Chagres crops out in a narrow belt along the Caribbean coast. The Toro limestone member consists of thin basal calcareous strata deposited in shallow water. These shallow-water deposits suggest that the formation did not extend much beyond its present inland border. The Chagres contains little tuffaceous material.
The moderately strong deformation of the pre-Gatun Tertiary formations is of regional extent, the results of the second regional deformation, but is not well dated. It may have taken place during early Miocene time or during Pliocene time after deposition of the Chagres sandstone. The Gatun formation and Chagres sandstone are only mildly deformed, but mild deformation in the Caribbean coastal area may have taken place at the same time as stronger deformation elsewhere.
Pleistocene deposits, characterized by much black organic material, are found in valleys that were cut in the Chagres standstone and older formations and later filled during submergence. Near the coast the Pleistocene strata include fossiliferous marine deposits.
Seventy-eight species and subspecies of Tertiary mollusks, representing 15 families of gastropods, are described and 13 others are recorded. Fifty of the 91 forms are from the Gatun formation. These 91 forms are estimated to represent about a seventh of the total available molluscan fauna in the marine Tertiary formations.
INTRODUCTION
HISTORICAL BACKGROUND
Marked advances in knowledge of the geology of the present Canal Zone coincide with three periods of active investigations bearing on construction of the canal or on proposed changes affecting it: French operations (1881-89 and 1895-99), American construction (190513), and Third Locks and Sea-level Conversion Route studies (1938-48).


With one exception, accounts of the geology that were published before French operations started are of historical interest only (Garella, 1845, 1849, pp. 519524; Wagner, 1861; Maack, 1874, pp. 164-167; Wyse, Reclus, and Sosa, 1879, pp. 153-163; Boutan, 1880). The exception is Boutan's account. His scientifically and historically important paper, published in 1880, a few years after the earliest description of the microscopic petrology of American rocks, was based on a microscopic examination at the Ecole de Mines of rocks he collected along the Panama Railroad just before French operations got under way. He also had a better idea of the age of the sedimentary rock formations than his predecessors. Chaper's report (1890), written during liquidation of the first French company, does not add much to Boutan's.
During the operations of the first French company collections of fossils were sent to the French paleontologist Henri Douvill6. His age assignments (Douvill6, 1891), published after liquidation of the first company, placed the geology on a firmer footing.
The most important publication during the period of French operations was prepared by the French geologist Marcel Bertrand in collaboration with a Swiss engineer who had worked on the canal, Philippe Ziircher (Bertrand and Znircher, 1899). It was based on the work done by the French companies and on a new set of age assignments by DouvillS (1898). The account by Bertrand and Zfrcher emphasized the following major features of the geology along the canal: the pyroclastic rocks and associated lavas southeast of the big bend in Rio Chagres at the present site of Gamboa are the oldest rocks; the strata overlying them are in general progressively younger toward both the Caribbean Sea and the Pacific Ocean; the fossiliferous strata are of Oligocene and Miocene age. The volcanic rocks are now thought to be of the same age as the oldest sedimentary formations along the shores of Gatun Lake. Otherwise Bertrand and Zfrcher's conclusions have been confirmed by later investigations and are accepted at the present time.
In the meantime R. T. Hill visited Panama in 1895, before the second French company resumed operations. He evidently did not have access to most of the subsurface records and there is no indication that he was aware of Douville's 1891 note. His report (1898) was supported by paleontologic work by Dall. Hill thought the oldest strata, probably pre-Tertiary, to be on the Pacific coast. Through some misfortune, one of his collections of fossils was mislabelled before it reached Dall's hands. As a result of the mislabelling, Dall referred part of the Gatun formation to the Eocene, an error that affected American geologic literature for many years.


2








Soon after American operations were started, Ernest Howe was employed by the Isthmian Canal Commission to study the geology. Though he was in the Canal Zone only five months during 1906 and 1907, his reports clearly set forth the essential features and went a long way toward systematizing the stratigraphic nomenclature (Howe, 1907, 1907a, 1908). Appointment of D. F. MacDonald, formerly of the U. S. Geological Survey, as resident geologist during the last two years of the construction period (1911-13) led to further advances and to the gathering of much information (MacDonald, 1913, 1913a, 1915, 1919). Only the first of the four publications by MacDonald just cited is generally cited on the following pages in the discussion of the stratigraphy. The others contain practically identical descriptions, aside from new names. Many of the fossils described in the present report were collected by MacDonald or by MacDonald and Vaughan, when Vaughan collaborated with him in the latter part of 1911. The stratigraphy, as worked out by MacDonald and Vaughan, was described in Bulletin 103 of the U. S. National Museum (Vaughan, 1919). Though Bulletin 103 was issued in 1919, many of its parts were published separately in 1918, and Jackson's part on the echinoids was issued separately in 1917 and again in 1918. In the preparation of Bulletin 103 Vaughan enlisted the services of a group of paleontologists, who described practically all the Canal Zone fossils then available in the National Museum collections, except the mollusks. Not all the fossils described in Bulletin 103 are mentioned in the summaries on the following pages. Calcareous algae (M. A. Howe, 1918), land plants (Berry, 1918), Bryozoa (Canu and Bassler, 1918), decapod crustaceans (Rathbun, 1918), and ,barnacles (Pilsbry, 1918) are omitted.
The third period of marked advances resulted from investigations, including the study of some 2,000 cores, of the Geological Section of the Special Engineering Division of the Panama Canal, carried out under the direction of T. F. Thompson. The surface and subsurface studies undertaken by this staff of geologists were for the most part directly related to the Third Locks and Sea-level Conversion Route projects. The published reports prepared by the Geological Section include summaries of the geology and more detailed descriptions of particular areas (Thompson, 1943, 1943a, 1944, 1947, 1947a). The oldest rocks, older than any along the canal, were found to consist of a basement of unknown age overlain by deposits of Eocene age. Agglomerate along the southeastern part of the canal, formerly correlated with agglomerate underlying the Culebra formation, overlies the Culebra. Marine deposits in the same region formerly identified


as the Culebra formation, also are younger than that formation.
PURPOSE AND SCOPE OF REPORT
The National Museum's collection of fossil mollusks from the Canal Zone represent a collecting span of a century. Not many collections, however, were received prior to 1911, when the fossils collected by MacDonald began to arrive. It was expected that the mollusks would be studied by W. H. Dall, the dean of American Tertiary invertebrate paleontologists. For the most part he got no further than generic identification of MacDonald's early collections. Therefore the mollusks-the most abundant fossils then availablewere omitted when Bulletin 103 was assembled. A considerable number of mollusks from the richly fossiliferous Gatun formation, collected while the canal was being constructed, were described by Toula (1909, 1911) and by Brown and Pilsbry (1911, 1913) before the publication of Bulletin 103. Other Gatun species have been recorded in scattered publications, and also a few from other formations (Culebra formation and its Emperador limestone member, Toro limestone member of Chagres sandstone). Nevertheless the National Museum collections represent much valuable information, which is not in useable form until the fossils are adequately studied. The present report is designed to meet that need.
The collections obtained before and during construction of the canal are especially valuable, for very few of them can be duplicated. Some of them, particularly in Gaillard Cut, represent excavated prisms of rock; many other localities are now submerged; still others are inaccessible through the rapid disintegration of rock and the rapid growth of a thick cover of vegetation.
To take advantage of the store of information gathered by the Geological Section of the Special Engineering Division, field work in the Canal Zone was undertaken during the dry season early in 1947. By that time it was evident that work in the fairly complete succession of lower and middle Tertiary marine formations in Panami east of the Canal Zone was needed to interpret the less complete partly marine succession of the same age in the Zone. Further field work was carried out early in 1949 and early in 1954. The work in 1954 was limited to Barro Colorado Island and nearby parts of the Gatun Lake area. The geology of Barro Colorado is to be described in a separate publication.
The field work was designed as a stratigraphic and paleontologic project-not as a mapping project, which would have been very time-consuming. Some kind of map, however, was needed to show the localities


INTRODUCTION


3







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


at which fossils were collected. A decision was reached to compile a geologic map, based on the material in the publications and files of the Geological Section of the Special Engineering Division, supplemented by scattered personal observations. The resulting map on the scale of 1:75,000, issued as a separate publication in 1955, is reproduced with minor alterations as plate 1 of the present report. The quality of the map is very uneven. Parts of it show the geology in considerable detail; other parts are greatly generalized and represent rapid reconnaissance. Despite its defects, however, it shows the geologic setting of the Canal Zone and adjoining parts of Panama. The only comparable map was published by MacDonald (1915, pl. 4; 1919, pl. 153) on a scale of about 1:260,000. The base used for the 1955 map does not show the recent suburban expansion of the city of Panamai.
At first the present report was planned to consist of a discussion of the stratigraphy, summaries of the occurrence of fossils other than mollusks, and description of the Tertiary mollusks. While the work was in progress, an incomplete carbon copy of a manuscript by MacDonald on the geology of Panami was found among Dall's effects at the U. S. National Museum. This report, prepared soon after MacDonald's tour of duty as resident geologist in the Canal Zone, was mentioned by MacDonald (1913, p. 579) and Vaughan (1919, p. v). It was not finished because Dall's work on the fossils was not completed. One of MacDonald's duties as resident geologist was to recommend rock for use as concrete aggregate, as armoring for breakwaters and earth dams, and for other construction purposes. In carrying out this assignment he examined outcrops of igneous rocks, studied thin sections of them, and arranged for chemical analyses of some of the rocks to be made in the chemical laboratory of the U. S. Geological Survey. His description of the rocks, which is more complete than his published notes, and the chemical analyses are included in his manuscript. They have been incorporated in the present report, although the analyses have already been published.
Though the present report includes more than stratigraphy and paleontology, the title-chosen for brevity-is too comprehensive. Many aspects of the geology are omitted or are only briefly considered. This report is, in fact, a progress report so far as the geology is concerned. Much of the area covered by plate 1 has not yet been studied and it may be a long time before the entire region is adequately studied.
The systematic paleontology deals with the mollusks in about 260 collections from all the fossiliferous Tertiary formations, which range in age from middle and late Eocene to early Pliocene. In chapter A, 78 species and subspecies of gastropods are described and 13 others


are recorded. These 91 forms are estimated to repre r sent about a seventh of the total available mollusca fauna to be described. Fifty of the 91 are from th Gatun formation, an indication of the size of the Gatun fauna.
Fuller discussion of the age and correlation of th formations is planned for the final part of the report That part also is to contain a discussion of the broade) aspects of the succession of faunas, including their bear ing on the history of the Panam6 land bridge and th light they shed on paleoecology.
ORTHOGRAPHY OF GEOGRAPHIC NAMES
Spanish orthography, including accent marks, is used for geographic names in Panam6. In the Canal Zone, however, many names of Spanish origin are anglicized and for such names accent marks are omitted. The major streams cross the boundary, and therefore "rio" or "quebrada" is used for all the streams that are named, regardless of location. The plan just outlined results in "Panamd" for the name of the country, the capital city, and a geologic formation, but "Panama Railroad" and "Panama Canal" for two features in the Canal Zone.
ACKNOWLEDGMENTS
Brig. General J. H. Stratton, (retired, then Col.), Supervising Engineer in charge of the Special Engineering Division, and T. F. Thompson, Chief of the Geological Section of the Division, placed every facility at my disposal during the field work in 1947, and Mr. Thompson again in 1949, when the Division had practically completed its work and its staff was greatly reduced. Mr. Thompson has a wide familiarity with the geology of the Canal Zone and Panama, which lie freely shared, and he guided me to many localities where' fossils are available. Other geologists of the Geological Section were very helpful. Special acknowledgment should be made to S. K. Bartholomew, L. H. Henderson, S. M. Jones, J. M. Matthews, T. G. Moran, J. R. Schultz, R. H. Stewart, J. A. Tavelli, and L. C. Woolfe.
The general geologic map (pl. 1) is based for the most part on material gathered by geologists of the Geological Section: principally a published map of the Gatun Lake area by S. M. Jones (1950, pl. 2); a map of the Quebrancha syncline by T. F. Thompson, a small part of which was published (Thompson, 1944); a map of an area east of Gamboa, between Rio Chagres and Madden Highway, by L. C. Woolfe; strip maps along the proposed sea-level canal (Thompson, 1947a, figs. 29-32); strip maps of the Chorerra route by J. R. Schultz. Mr. Thompson and Mr. Stewart offered valuable suggestions for filling in gaps. I, however, must assume responsibility for the map's shortcomings,


4








which will become apparent as additional work is done. G. E. Lewis, of the U. S. Geological Survey, and J. G. /Marks, of Creole Petroleum Corporation, assisted in preparation of the Spanish explanation. The sealevel canal strip maps already mentioned were used for the more detailed map of the Gaillard Cut area (pl. 2). The field photographs, from the files of the Special Engineering Division, are available through the kindness of Mr. Thompson.
Large faunas of smaller Foraminifera from the Gatuncillo and Bohio formations, collected in 1947 and 1949, were identified by H. H. Renz and P. J. Bermudez, both of Caracas, Venezuela. Larger Foraminifera collected at the same time were identified by W. S. Cole, of Cornell University and the U. S. Geological Survey (Cole, 1952 (1953)); corals by J. W. Wells, of Cornell University and the U. S. Geological Survey; echinoids by C. W. Cooke, of the U. S. Geological Survey (Cooke, 1948). M. N. Bramlette, of the Scripps Institution of Oceanography and the U. S. Geological Survey, furnished notes on smaller Foraminifera found in the Caimito and Culebra formations and in the La Boca marine member of the Panami' formation. R. A. Stirton, of the University of California, kindly furnished drawings of a mammal bone and comments concerning that interesting fossil. Samples of lava and tuff from the basement complex were examined by W. S. Burbank, of the U. S. Geological Survey, who also kindly read the part of the report dealing with the igneous rocks.
Extensive collections of mollusks from the Gatun formation, deposited at Stanford University by Mr. Thompson, were generously loaned by Miss A. Myra Keen. For permission to examine types and other specimens I am indebted to H. A. Pilsbry, A. A. Olsson, and Miss Anne Harbison, of the Academy of Natural Sciences of Philadelphia; W. S. Cole, of Cornell University; the late G. D. Harris, of the Paleontological Research Institution; J. W. Durham, of the University of California; and L. G. Hertlein, of the California Academy of Sciences. For much advice I am indebted to H. A. Reader, of the U. S. National Museum, and R. T. Abbott, formerly of that institution, where this work was carried out.
ANNOTATED BIBLIOGRAPHY
The following briefly annotated bibliography lists publications on the geology and paleontology of the Canal Zone and adjoining parts of Panam'. It includes publications containing information on those subjects, though the publications are primarily devoted to other areas. With three exceptions, it does not include publications on engineering aspects of construction of
413788-57-2


the canal-notably on the canal slides-despite mention or discussion of geologic features. The three exceptions are MacDonald's U. S. Bureau of Mines Bulletin 86, issued in 1915, the National Academy of Sciences 1924 report on slides, and MacDonald's 1947 posthumous publication on the same subject. No attempt has been made to glean incidental geologic observations from early literature. A great number of travelers crossed the isthmus during the California gold rush, first by boat up Rio Chagres to Las Cruces (a short distance above the present site of Gamboa) and thence by muleback, and later by the Panama Railroad, which was completed in 1855. Some of the travelers who wrote about their journey in books or nongeologic periodicals may have recorded observations on the geology.
1845. Garella, Napolon, Projet d'un canal de jonction de
l'Octan Pacifique et de l'Oc6an Atlantique h travers
l'isthme dc Panama, 233 p., maps, profiles, Paris.
Chapter 4 (p. 35-46), "Aperqu gtologiqar seer in
constitution des terrains de l'isthne", is generalized and of little interest. The 1:200,000 hachured topographic map, prepared in 1844, is an important
historical document.
1849. Garella, Napolson, Project of a canal to connect the
Atlantic and Pacific oceans across the Isthmus of Panama: U. S. 30th Cong., 2nd sess., House Rept.
145, p. 506-590, maps, profiles.
Translation of preceding publication.
1853. Moore, J. C., Notes on the fossil Mlollusca and fish from
San Domingo: Geol. Soc. London Quart. Jour.,
v. 9, p. 129-132.
A note at the end of this paper (p. 132) is the first
record in a scientific journal of the discovery of Miocene fossils in the present Canal Zone. The fossils were found "about 2% miles from the shores of Navy Bay [Lisoon Bay] * in a cutting of the
Panama Railway" [near Mindi].
1855. Deck, Isiah, Notes on the geological features of the
Panama Railroad: Mining Mag., v. 4, p. 240-245,
New York.
Fossils were observed at Monkey Hill [Moeunt
Hope] but not at Gatun.
1855. Conrad, T. A., Report on the fossil shells collected in
Californea by Win. P. Blake, geologist of the expedition under the command of Lieutenant R. S.
Williamson, United States Topographical Engineers; appendix to the preliminary geological report of William P. Blake: U. S. Pacific R. R. Expl., U. S.
33rd Cong., 1st sess., House Ex. Doe. 129, p. 5-20.
Includes three species of mollusks collected by
Blake. The type of one species (Gratelupia? mactropsis) is in the National Museum.
1857. Blake, W. P., Geological report [Williamson's reconnaissance in California]: U. S. Pacific R. R. Expl., v. 5,
pt. 2, 370 p., 11 pls., maps, sections.
Observations on trip across Panamn are recorded
(p. 1-2). A few fossils were collected 'at Gatun, or Monkey Hill?." The species indicate they were
collected at Gatun.


3


INTROD UCTION








GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


1857. Conrad, T. A., Descriptions of the fossil shells [Williamson's reconnaissance in California]: Idem, app.,
art. 2, p. 317-329, pls. 2-9.
Conrad's 1855 descriptions are repeated and poor
illustrations are added.
1857. Conrad, T. A., Description of the Tertiary fossils collected on the survey [Williamson's survey in California and
Oregon]: Idem, v. 6, pt. 2, p. 69-73, pls. 2-5.
Includes five species of mollusks collected by
Newberry at Gatun.
1861. Wagner, Moritz, Beitrdge zu einer physisch-geographischen Skizze des Isthmus von Panama: Petermanns
Mitt., Ergdnzungsheft 5, 25 p., map.
Geologic observations are incidental and unimportant. Reddish conglomerate and fragmental
rocks at city of Panamd are assigned to Permian. 1874. Maack, G. A., Report on the geology and natural history of the isthmuses of Choco, of Darien, and of Panama, in Selfridge, T. 0., Reports of explorations and surveys to ascertain the practicability of a ship-canal between the Atlantic and Pacific Oceans by the way of the Isthmus of Darien, p. 155-175, Washington.
Geologic observations along Panama Railroad
(p. 164-167) are inconsequential. Maack, like Wagner, suggested a Permian age for red conglomerate at Panam.
1879. Wyse, L. N. B., Reclus, Armand, and Sosa, P., Rapports
sur les 6tudes de la commission internationale d'exploration de l'isthme am6ricain, 294 p., 2 maps,
Paris.
Account of geology along route of proposed canal,
like earlier accounts, is of historical interest only.
List of rocks collected (p. 279-280) was prepared by
Daubr6e.
1880. Boutan, E., Note sur la constitution g6ologique de
l'isthme de Panama: Annales de Mines, 7th ser.,
t. 18, p. 5-58, 2 pls. (map and profiles).
Interesting account of geology along route of
proposed canal, based on microscopic examination, at Ecole des Mines, of rocks collected along Panama
Railroad.
1881. Gabb, W. M., Descriptions of Caribbean Miocene fossils:
Acad. Nat. Sci. Philadelphia Jour., 2d ser., v. 8,
p. 337-348, pls. 44, 45.
Includes eight species of mollusks collected by
Newberry at Gatun.
1886. Wyse, L. N. B., Le canal de Panama, 399 pp., maps,
woodcuts, Paris.
Discussion of geology (pp. 12-20) is drawn from
earlier accounts. Fossils at scattered localities are mentioned. Shaded relief map of canal route is on
scale of 1:100,000.
1890. [Chaper, ], Description g6ologique des terrains
traverses par le canal: Commission d'6tudes institu6e par le liquidateur de la compagnie universelle,
Rapport 6, 30 p., Paris.
According to Douvill6 (1898, p. 589, footnote),
Chaper, an engineer of the first French company, wrote this account. It does rot add much to Boutan's. Black fossiliferous limestone at Vamos
Vamos, however, is mentioned.
1890- Dall, W. H., Contributions to the Tertiary fauna of 1903. Florida: Wagner Free Inst. Sci. Trans., v. 3, 6 pts.,
1,654 p., 60 pls.


Includes mollusks from Vamos Vamos, Gatun,
and Monkey Hill [Mount Hope].
1891. Douvill6, Henri, Sur i'Age des couches traverses par le
canal de Panama: Acad. Sci. Paris Compte Rendu,
t. 112, p. 497-499.
First modern age assignments. The fossiliferous
strata are assigned to Oligocene and Miocene.
1896. Guppy, R. J. L., and Dall, W. H., Descriptions of
Tertiary fossils from the Antillean region: U. S.
Natl. Mus. Proc., v. 19, p. 303-331, pls. 27-30.
Includes two species of mollusks from Gatun and
Monkey Hill [Mount Hope].
1898. Hill, R. T., The geological history of the Isthmus of
Panama and portions of Costa Rica: Mus. Comp.
Zool. Harvard College Bull., v. 28, p. 151-285,
19 pls., 24 figs.
Geology of Panasna Railroad and French canal. 1898. Douvill6, Henri, Sur l'Age des couches traverses par
le canal de Panama: Soc. G6ol. Fronce Bull., 3me
ser., t. 26, p. 587-600.
Some of Douvill6's 1891 age assignments are
changed; others are reinforced by additional data. 1899. Bertrand, Marcel, and Zfrcher, Philippe, Etude g6ologique sur l'isthme de Panama: Compagnie Nouvelle du Canal de Panama, Rapport de la Commission,
app. 1, p. 83-106, map, structure sections, Paris.
Most satisfactory of earlier accounts of geology of
canal route. The map (scale 1:100,000), which has 10-meter (or several tens of meters) contours along route of canal and up Rio Chagres to Alhkjuela, is
the last and the best of the French maps.
1899. Bouvier, E. L., Calappa zurcheri, crabe nouveau des
terrains mioctnes de Panama: Mus. Hist. Nat.
Paris Bull., t. 5, p. 189-192, 1 fig.
Locality where this fossil was found is not specified. 1901. Hershey, 0. H., The geology of the central portion of the
Isthmus of Panama: Calif. Univ., Dept. Geol.,
Bull., v. 2, p. 231-267, map.
Panamd formation at and near Panamd is briefly
mentioned (p. 245-246). Hershey's age assignments
are much too old.
1904. Cushman, J. A., Pleistocene foraminifera from Panama:
Am. Geologist, v. 33, p. 265-266.
List of 14 species from a locality near Mindi. 1904. Lemoine, P., and Douvil]6, R., Sur le genre Lepidocyclina
Gnlmbel: Soc. G6ol. France M6m. 32 (t. 12), p. 1-42,
pls. 1-3.
Includes Lepidocyclina chaperi and L. canellei,
both named for engineers of first French company. 1907. Howe, Ernest, Report on the geology of the Canal Zone:
Isthmian Canal Comm., Ann. Rept., 1907, app. E,
p. 108-138, pl. 147.
Principal features of Canal Zone geology.
1907. Howe, Ernest, Isthmian geology and the Panama Canal:
Econ. Geology, v. 2, p. 639-658, pl. 8.
Economic aspects of geology are emphasized. 1908. Howe, Ernest, The geology of the Isthmus of Panama:
Am. Jour. Sci., 4th ser., v. 26, p. 212-237.
Stratigraphy and paleontology are emphasized. 1909. Toula, Franz, Eine jungtertidre Fauna von Gatun am
Panama-Kanal: K. k. Geol. Reichsanstalt Jahrb.,
Band 59, p. 673-760, pls. 25-28, 15 figs.
Mollusks, otoliths, and a few other fossils from
Gatun formation, mostly from Gatun Locks site
and spillway of Gatun Dam.


6







INTRODUCTION


1911. Brown, A. P., and Pilsbry, H. A., Fauna of the Gatun
formation, Isthmus of Panama: Acad. Nat. Sci.
Phila. Proc., v. 63, p. 336-373, pls. 22-29.
Mollusks from Gatun Locks site, one of which also
occurs at Monkey Hill [Mount Hope].
1911. Toula, Franz, Die jungtertire Fauna von Gatun am
Panama-Kanal; 2. Teil: K. k. Geol. Reichsanstalt
Jahrb., Band 61, p. 487-530, pls. 30, 31.
Mollusks and a few coral, echinoid, and crab
remains.
1912. Dall, W. H., New species of fossil shells from Panama
and Costa Rica: Smithsonian Misc. Coll., v. 59,
no. 2, 10 p., March, 1912.
Includes 11 species of Pleistocene mollusks
collected near Mount Hope and 1 species and variety collected at Toro Point [Toro limestone member of
Chagres sandstone].
1912. de Boury, E., in Cossmann, M., Essais de paldoconchologie compare t. 9, 215 p., 10 pls., August, 1912.
The fossil from Toro Point described by Dall five
months earlier as Epitonium (Sthenorytis) toroense is described by de Boury as Stenorhytis chaperi (p.
177).
1913. de Boury, E., Catalogue raisonn6 de la collection de
Scalaria vivants et fossiles du Mus6um de Paris: Mus. Hist. Nat. Paris Nouv. Arch., 5me ser., t. 4,
p. 209-266, pis. 12-16.
Includes another description of Stenorhytis chaperi
(p. 252).
1913. Brown, A. P., and Pilsbry, H. A., Fauna of the Gatun
formation, Isthmus of Panama; pt. 2: Acad. Nat.
Sci. Phila. Proc., v. 64, 1. 500-519, pls. 22-26, 5 figs.,
1912 (1913).
Mollusks from Gatun formation, from "the Pecten
bed at tower N, Las Cascadas" [Emperodor limestone member of Cuelbra formation], and mollusks and a crab from "the lignitic layers near tower N,
Las Cascadas" [Culebra formation proper].
1913. Brown, A. P., and Pilsbry, H. A., Two collections of
Pleistocene fossils from the Isthmus of Panama:
Idem, v. 65, p. 493-500, 3 figs,
Numerous Pleistocene mollusks and a barnacle
collected near Mount Hope and at north end of Gatun Locks are listed, and 6 species and subspecies
of mollusks are described.
1913. MacDonald, D. F., Geology of the Isthmus: Canal
Record, v. 6, no. 27, p. 213-215, Feb. 26, 1913.
A preliminary account. Stratigraphic nomenclature is same as in next item, but it would be inappropriate to cite a weekly periodical of limited
distribution for new stratigraphic Dames.
1913. MacDonald, D. F., Isthmian Geology: Isthmian Canal
Comm., Ann. Rept., 1913, app. S, p. 564-582, pis.
65-77.
With exception of names published later, this publication is cited in present report for MacDonald's stratigraphic geology. Published in latter part of
1913; transmittal of volume is dated Sept. 15.
1913. MacDonald, D. F., Geologic section of the Panama
Canal Zone (abstract): Geol. Soc. America Bull.,
v. 24, p. 707-710.
Aside from omission of first two paragraphs, this
is a republication of the earlier "Canal Record"
account.


7


1913. Cossmana, M., Etude comparative defossiles mioenniques
recueillis A la Martinique et A l'isthme de Panama:
Jour. Conchyliologie, t. 61, pp. 1-64, pls. 1-5.
Includes mollusks from Gatun formation at Mindi
and Monkey Hili [Mount Hope].
1915. Douvill6, Henri, Les couches A orbitoides de l'isthme de
Panama: Soc. G6bo. France Compte Rendu Som.,
1915, no. 16, p. 129-131.
Oligocene age of limestone on upper Chagres
[Gatuncillo formation] is reiterated, despite presence of a discocyclinid. Strata at Pea Blanca [Caimito formation] and Pedro Miguel [probably Culebra formation] are considered to be of Aquitanian age. 1915. MacDonald, D. F., Some engineering problems of the
Panama Canal in their relation to geology and topography: U. S. Bur. Mines Bull. 86, 88 p., 29 pls.,
9 figs.
The name "Toro limestone" is proposed. Description of some formations is more detailed than in
MacDonald's earlier publications.
1917. Sheldon, P. G., Atlantic slope Arcas: Palaeontographica
Americana, v. 1, no. 1, p. 1-101, pls. 1-16.
A new name, Arcea balboai (p. 69), is proposed for
a species from Culebra formation.
1917. Jackson, R. T., Fossil echini of the Panama Canal Zone
and Costa Rica: U. S. Natl. Sius. Proc., v. 53, p.
489-501, pls. 62-68, 4 figs.
Echinoids from Emperador limestone [member of
Culebra formation] and Gatun formation.
1918. Howe, M. A., On some fossil and Recent Lithothamnieae
of the Panama Canal Zone: U. S. Natl. Mus. Bull.
103, p. 1-13, pls. 1-11.
Calcareous algae from Cainito formation [misidentified as Culebra formation and Emperador limestone member] and Pleistocene deposits. Reissued in complete volume, 1919.
1918. Berry, E. W., The fossil higher plants from the Canal
Zone: Idem, p. 15-44, pls. 12-18.
Plants from Boilo, Culebra, Cucaracha, and
Gatun formations. Reissued in complete volume,
1919.
1918. Cushman, J. A., The smaller fossil Foraminifera of the
Panama Canal Zone: Idena, p. 45-87, pls. 19-33.
Foraminifera from Caimito [misidentified as
Culebra] and Culebra formations, Emperador limestone member of Culebra formation, La Boco marine member of Panamd formation [misidentified as Culebra formation], Gatun formation, and Pleistocene strata. Reissued in complete volume, 1919. 1918. Cushman, J. A., The larger fossil Foraminifera of the
Panama Canal Zone: Idem, p. 89-102, pis. 34-45.
Foraminifera from Caimito formation [misidentified as Culebra formation and Emperador limestone member], Culebra formation and Emperador limestone member, and La Boca marine member of Panami formation [misidentified as Culebra formation]. Reissued in complete volume, 1919.
1918. Jackson, R. T., Fossil echini of the Panama Canal Zone
and Costa Rica: Idem, p. 103-116, pls. 46-52,
figs. 1-3.
Reissue, with slight changes, of 1917 publication
having same title. Reissued in complete volume,
1919.







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


1918. Canu, Ferdinand, and Bassler, R. S., Bryozoa of the Canal Zone and related areas: Idem, p. 117-122,
pl. 53.
Two species from Emperador limestone [member
of Culebra formation]. Reissued in complete
volume, 1919.
1918. Rathbun, M. J., Decapod crustaceans from the Panama region: Idem, p. 123-184, pls. 54-66.
Species from Caimito [misidentified as Culebra],
Culebra, and Gatun formations, and Pleistocene
strata. Reissued in complete volume, 1919.
1918. Pilsbry, H. A., Cirripedia from the Panama Canal Zone: Idem, p. 185-188, pl. 67.
Five species from so-cllled Pliocene [Alhajuela
sandstone member of Caimito formation], Gatun formation, and Pleistocene strata. Reissued in
complete volume, 1919.
1919. Vaughan, T. W., Contributions to the geology and paleontology of the Canal Zone, Panama, and geologically related areas in Central America and the West Indies: U. S. Natl. Mus. Bull. 103, 612 p., 154 pls.,
27 figs.
Separate parts of this volume are listed in present
bibliography as 1918 or 1919 items.
1919. Vaughan, T. W., Fossil corals from Central America,
Cuba, and Porto Rico, with an account of the American Tertiary, Pleistocene, and Recent coral reefs:
Idem, p. 189-524, pis. 68-152, figs. 4-25.
Species front Caimito formation [misidentified as
Culebra formation and Emperador limestone member], Culebra formation and Emperador limestone member, and La Boca marine member of Panamd formation [misidentified as Emperador limestone member of Culebra formation] are described, and
species from Pleistocene strata are listed.
1919. MacDonald, D. F., The sedimentary formations of the
Panama Canal Zone, with special reference to the stratigraphic relations of the fossiliferous beds:
Idem, p. 525-545, pls. 153, 154, figs. 26, 27.
The name "Ciagres sandstone" is proposed.
Aside from that new name and slight changes in some age assignments, discussion of stratigraphy is essentially similar to that in MacDonald's 1915 account. Includes measured stratigraphic sections. 1919. Vaughan, T. W., The biologic character and geologic correlation of the sedimentary formations of Panama in their relation to the geologic history of Central
America and the West Indies: Idem, p. 547-612.
Paleontology, age, and correlation of formations
in Canal Zone.
1919. Sears, J. D., Deposits of manganese ore near Boqueron
River, Panama: U. S. Geol. Survey Bull. 710, p.
85-91, figs. 1-3.
Manganese prospects near Rio Boquer6n. Southernnost prospect is shown on plate 1 of present
report.
1921. Berry, E. W., A palm nut from the Miocene of the Cana
Zone: U. S. Natl. Mus. Proc., v. 59, p. 21-22, 3
figs.
Found in Gatun formation.
1921. Cooke, C. IV., Orthaulax, a Tertiary guide fossil: UT. S.
Geol. Survey Prof. Paper 129, p. 23-37, pls. 2-5.
Orthaulax gabbi is recorded from Caimito formation [not so specified] and Culebra formation.


1922. Olsson, A. A., The Miocene of northern Costa Rica::
Bull. Am. Paleontology, v. 9, no. 39, 309 p., 32 pis.,
Includes mollusks from Gatun formation of Canal I
Zone and one species from Toro limestone member.
of Chagres sandstone (Pecten macdonaldi).
1923. Vaughan, T. W., Studies of the larger Tertiary foraminifera from tropical and subtropical America: Natl.
Acad. Sci. Proc., v. 9, p. 253-257.
Includes Lepidocyclina miraflorensis from a incality, apparently now submerged, evidently representing La Boca marine member of Panamd
formation.
1924. Hanna, G. D., Rectifications of nomenclature: Calif.
Acad. Sci. Proc., 4th ser., v. 13, p. 151-186.
Three new names are proposed for Canal Zone
fossil mollusks.
1924. National Academy of Sciences, Report of the Committee
of the National Academy of Sciences on Panama Canal Slides: Natl. Acad. Sci. M~em., v. 18, 84 p.,
51 pls., 19 figs.
Appendix B on geology, by MacDonald, includes
structure sections of part of Gaillard Cut. Appendix C is a discussion of chemical and physical properties of Cucaracha formation.
1924. Vaughan, T. W., American and European Tertiary
larger Foraminifera: Geol. Soc. America Bull., v.
35, p. 785-822, pls. 30-36, 6 figs.
Includes Miogypsina cushmani, from Culebra formation, and M. panamensis from strata now referred
to Caimito formation.
1924- Douvill6, Henri, Revision des Lcpidocyclines: Soc. G6l. 1925. France Mc6m., new ser., 956m. 2 (t. 2), 115 p., 7
pls., 83 figs.
Includes Lepidocyclina canellei and L. chaperi,
and a new species from upper valley of Rio Chagres, L. decorate, which has not been recognized ir later
collections (see Cole, 1952, [1953], p. 3).
1925. Dali, W. H., Illustrations of unfigured types of shells in
the collections of the United States Nacional Museum: U. S. Natl. TMus. Proc., v. 66, art. 17, 41 p.,
36 pls.
Includes a Pliocene species (Sthenorytis toroense)
and two Pleistocene species (Corbula macdonaldi and
Yoldia perprotracla) described by Dall in 1912. 1925. Maury, C. J., A further contribution to the paleontology
of Trinidad (Miocene horizons): Bull. Am. Paleontology, v. 10, no. 42, 250 p., 43 pls.
Includes a species froin Culebra formation (Scapharca balboai) and two from Gatun formation
(Scapharca dariensis and Clementia dariena).
1926. Hodson, Floyd, Venezuelan and Caribbean Turritellas:
Idem, v. 11, no. 45, 50 p., 30 pls.
Turritella altilira is illustrated.
1926. Vaughan, T. W., The stratigraphic horizon of the beds
containing Lepidocyclina chaperi on Haut Chagres,
Panama: Natl. Acad. Sci. Proc., v. 12, p. 519-522.
At type locality, San Juan de Pequenc in sipper
Chagres valley (locality 3 of present report), Lepidocyclina chaperi is associated with ipper
Eocene species.
1926. Woodring, W. P., American Tertiary mollusks of the
genus Clementia: U. S. Geol. Survey Prof. Paper 147,
p. 25-47, pls. 14-17, 1 fig.


8








INTRODUCTION


Includes Clementia dariena, which occurs in Gatun
formation and is doubtfully recorded from Culebra
formation.
1927. Vaughan, T. W., Larger Foraminifera of the genus Lepidocyclina related to Lepidocyclina mantelli: U. S.
Nati. Mus. Proc., v. 71, art. 8, 5 p., 4 pls.
Includes Lepidocyclina miraflorensis.
1927. Palmer, K. V. W., The Veneridae of eastern America, Cenozoic and Recent: Palaeontographica Americana, v. 1, no. 5, 428 p., 45 pls.
Includes described fossil species from the Canal
Zone.
1927. Hodson, Floyd, Hodson, H. K., and Harris, G. D.,
Some Venezuelan and Caribbean mollusks: Bull.
Am. Paleontology, v. 13, no. 49, 160 p., 40 pls.
Includes species from Gatun formation.
1929. Anderson, F. M., Marine Miocene and related deposits
of north Colombia: Calif. Acad. Sci. Proc., 4th ser.,
v. 18, no. 4, p. 73-213, pis. 8-23.
Includes mollusks collected from Gatun formation
at spillway of Gatun Dam.
1930. Li, Chih Chang, The Miocene and Recent Mollusca of
Panama Bay: Geol. Soc. China Bull., v. 9, p. 249279, 8 pls., map.
Includes species characteristic of Gatun formation, stated to have been dredged at Pacific entrance
to canal.
1930. Rutsch, R., Einige interessante Gastropoden aus dem
Tertidr der Staaten Falc6n und Lara (Venezuela): Eclogae Geol. Helvetiae, Band 23, p. 604-614, pl. 17.
Type of Distorsio gatunensis is discussed and
illustrated.
1930. Reeves, Frank, and Ross, C. P., A geologic study of the
Madden Dam project, Alhajuela, Canal Zone: U. S.
Geol. Survey Bull. 821, p. 11-49, pls. 4-13, figs. 1-5.
Geology of Madden Dam site and area to be
flooded by Madden Lake.
1931. Pilsbry, H. A., The Miocene and Recent Mollusca of
Panama Bay: Acad. Nat. Sci. Phila. Proc., v. 83,
p. 427-440, pl. 41, 3 figs.
Eight of the species described by Li in 1930 are
Miocene fossils. One (Clementia dariena) is labelled "Gatun Locks and Spillway" and all have matrix characteristic of Gatun formation at and near Gatun. 1931. Hodson, Floyd, and Hodson, H. K., Some Venezuelan
mollusks: Bull. Am. Paleontology, v. 16, no. 59,
94 p., 24 pls.
Includes Macoa gatunensis.
1932. Vaughan, T. W., and Cole, W. S., A new species of
Lepidocyclina from the Panama Canal Zone: Washington Acad. Sci. Jour., v. 22, p. 510-514, 9 figs.
Lepidocyclina pancanalis is described. The type
locality, which is also the type locality of Miogypsina panamensis and Nummulites panamensis, represents Caimito formation, but is not so specified [locality
56 of present report].
1933. Vaughan, T. W., Studies of American species of Foraminifera of the genus Lepidocyclina: Smithsonian
Misc. Coll., v. 89, no. 10, 53 p., 32 pls.
Includes Lepidocyclina canellei and L. vaughani. 1934. Collins, R. L., A monograph of the American Tertiary
pteropod mollusks: Johns Hopkins Univ., Studies
in Geology, no. 11, p. 137-234, pls. 7-14.
Includes a species from Gatun formation, Vaginella caribbeana.


9


1936. Tucker, H. I., The Atlantic and Gulf coast Tertiary Pectinidae of the United States: Am. Midland
Naturalist, v. 17, p. 471-490, 4 pis.
Includes Pecten macdonaldi, from Toro limestone
member of Chagres sandstone.
1937. Coryell, H. N., and Embich, J. R., The Tranquilla shale (upper Eocene) of Panama and its foraminiferal fauna: Jour. Paleontology, v. 11, p. 289-305, pls.
41-43, 1 fig.
Foraminifera from a locality on RIo Chagres,
now flooded by Madden Dam.
1937. Coryell, H. N., and Fields, Suzanne, A Gatun ostracode
fauna from Cativa, Panama: Am. lus. Novitates
956, 18 p., 47 figs.
Ostracodes from lower part of Gatun formation. 1941. Vaughan, T. W., and Cole, Wi. S., Preliminary report on
the Cretaceous and Tertiary larger Foraminifera of Trinidad, British West Indies: Geol. Soc. America
Special Paper 30, 137 p., 46 pls., 2 figs.
Includes Operculinoides panaensis.
1941. Merriam, C. W., Fossil Turritellas from the Pacific coast
region of North America: Calif. Univ., Dept. Geol.
Sci., Bull., v. 26, no. 1, p. 1-214, pls. 1-41, 19 figs.
Turritella altilira is illustrated.
1942. Olsson, A. A., Tertiary deposits of northwestern South
America and Panamd: Eighth Am. Sci. Cong. Proc.,
v. 4, p. 231-287.
Tertiary formations of Panami.
1943. [Thompson, T. F.], Geology: Panama Canal, Dept. Operation and Maintenance, Special Eng. Div., Third
Locks Project, pt. 2, chap. 3, 33 p., 21 figs.
General discussion of geology of Canal Zone. 1943. [Thompson, T. F.], Foundations and slopes: Idem, pt. 2,
chap. 5, 138 p., 6 pls., 136 figs.
Detailed geology of Third Locks sites.
1944. Thompson, T. F., Geological explorations in the vicinity
of Rio Quebrancha for the Panama Cement Company: Panama Canal, Dept. Operation and Maintenance, Special Eng. Div., 34 p., 10 pls., 4 figs.
Geology of part of Quebrancha syncline, east of
Canal Zone.
1945. Nicol, David, Restudy of some Miocene species of
Glycymeris from Central America and Colombia:
Jour. Paleontology, v. 19, p. 622-624, pl. 85.
Includes Glycymeris canalis.
1946. Vaughan, T. W., Initiation of geological investigations in
the Panama Canal Zone: Science, v. 104, no. 2696,
p. 209.
Geologic investigations during construction period
after 1910 are attributed to a suggestion from
Lord Bryce to President Taft.
1946. Keen, A. M., and Thompson, T. F., Notes on the Gatun
formation (Miocene), Panama Canal Zone (abstract):
Geol. Soc. America Bull., v. 57, p. 1,260.
Three faunal zones are recognized.
1947. Nicol, David, Tropical American species of Glycymeris
from the Tertiary of Colombia, and a new species from Panama: Jour. Paleontology, v. 21, p. 346-350,
pl. 50.
Includes Glycymeris schenchi from Gatun formation.
1947. MacDonald, D. F., Panama Canal slides: Panama Canal,
Dept. Operation and Maintenance, Special Eng.
Div., Third Locks Project, 73 p., 52 pls., 5 figs.








GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


A posthumous publication. Discussion of geology
includes some modification of MacDonald's earlier views. Geology of slide area in Gaillard Cut is
shown on detailed map (scale, 1 inch=465 feet). 1947. [Thompson, T. F.J, Geology: Panama Canal, Rept.
Governor under Public Law 280, 79th Cong., 1st
Sess., Annex 3, 30 p., 8 figs.
Geology of proposed sea-level canal is summarized. 1947. [Thompson, T. F.], Geology: Idem, App. 8, 84 p., 38 figs.
Geology of proposed sea-level canal. Areal geology
is shown on strip maps, scale 1:40,000 and 1:20,000. 1948. Cooke, C. W., Eocene echinoids from Panama: Jour.
Paleontology, v. 22, p. 91-93, pl. 22.
Eocene echinoids collected in Madden basin during
field work for present report.
1949. Woodring, W. P., and Thompson, T. F., Tertiary formations of Panama Canal Zone and adjoining parts of Panama: Am. Assoc. Petroleum Geologists Bull.,
v. 33, p. 223-247, 2 figs.
Summary of stratigraphy and paleontology of
Tertiary formations.
1949. Cole, W. S., Upper Eocene larger Foraminifera from the
Panama Canal Zone: Jour. Paleontology, v. 23, p.
267-275, pls. 52-55.
First published record of Eocene deposits in Canal
Zone. The fossils were collected at locality 29 of
present report.
1949. Bermddez, P. J., Pavoninoides, a new genus of the Miliolidae from Panama: Cushman Lab. Form. Research
Contr., v. 25, pt. 3, p. 58, 1 fig.
Pavoninoides panamensis, from "marly limestone
of the Oligocene (probably middle), Madden Lake."
Though the locality is indefinite, the limestone presumably is in Gatuncillo formation.
1949. Rubio, Angel, Notas sobre geologla de Panamd: Panam6,
Ministerio de Educacisn, Depto. de Cultura y Publicaciones, 183 p., 32 figs.
Compilation of data on geology of Panamfi.
1950. Pilsbry, B. A., and Olso, A. A., Review of Anticlimax,
with new Tertiary species (Gastropoda, Vitrinellidae): Bull. Am. Paleontology, v. 33, no. 135, 22
p., 4 pls.
Includes Anticlimax gatunensis and A. teleospira,
from lower part of Gatun formation.
1939. Jones, S. M., Geology of Caun Lake used vicinity,
Panama: Geol. Soc. America Bull., v. 61, p. 893-922
2 pls., 2 figs.
Geology of Gatun Lake area. Includes a geologic map, scale 1:125,000.
1952. Drooger, C. W., Study of American Miogypsinidae, 80
p., 3 pis., 14 figs., Zeist, Netherlands.
Includes species from Caisnito formation and
Culebra formation, including Emperador limestone
member.
1952. Thompson, T. F., Ring dikes of the continental divide
region, Panama Canal Zone (abstract): Geol. Soc.
America Bull., v. 63, p. 1396, 1992.
Ring-shaped and cup-shaped dikes surrounding
hills of agglomerate ie Gaillard Cut area.
1953. Cole, W. S., Eocene and Oligocene larger Foraminifera
from the Panama Canal Zone and vicinity: U. S.
Geol. Survey Prof. Paper 244, 41 p., 28 pls., 2 figs.,
1952 [19531.
Eocene and Oligocene larger Foraminifera collected during field work for present report.


1953. Cole, W. S., Some late Oligocene larger Foraminifera from
Panama: Jour. Paleontology, v. 27, p. 332-337, pls.
43, 44.
Species in MacDonald's collections from Culebra
formation, including Emperador limestone member, and La Boca marine member of Panamd formation. 1954. Bramlette, M. N., and Riedel, W. R., Stratigraphic value
of discoasters and some other microfossils related to Recent coccolithophores: Jour. Paleontology, v. 28,
p. 385-403, pls. 38-39, 3 figs.
Includes records of discoasters from Gatuncillo
and Culebra formations.
1955. Woodring, W. P., Geologic map of Canal Zone and adjoining parts of Panamg,: U. S. Geol. Survey, Misc.
Geol. Invest., Map I-1, scale 1:75,000.
Reproduced with minor alterations as plate 1 of
present report.
1956. Terry, R. A., A geological reconnaissance of Panama:
Calif. Acad. Sci. Occasional Paper 23, 91 p., 3 pls.,
8 figs.
A general account of the geology of Panam,
including Canal Zone. Published after present
report was prepared.
1957. Cole, W. S., Late Oligocene larger Foraminifera from
Barro Colorado Island, Panama Canal Zone: Bull.
Am. Paleontology, v. 37, no. 163, p. 309-338, pls.
24-30.
Description of species from Bohio and Caimito
formations of Barro Colorado Island.

GEOLOGY
STRATIGRAPHY
OUTLINE OF STRATIGRAPHY
The region covered by plate 3 embraces all except the extreme western part of a Tertiary marine sedimentary area which may be designated the central Panama area (fig. 1). The boundaries of the areas shown in figure 1 represent the approximate known e_:tent of Tertiary marine formations, not the outlines of depositional basins. In the central PanamA area, Tertiary marine formations extend across the continental divide.
The stratigraphy in the region covered by plate 1 is notably different from place to place. For the purpose of description six main regions are recognized: Quebrancha syncline, Madden basin, Gatun Lake area, Caribbean coastal area, Gaillard Cut area, Pacific coastal region in Panamn east of the Canal Zone. Quebrancha syncline and Madden basin are structural features east of the Canal Zone. Gaillard Cut, designated Culebra Cut during the construction period, is the part of the canal excavation beginning opposite the south end of the Panama Railroad bridge across Rio Chagres at Gamboa and extending southeastward, across the continental divide, to the north end of Pedro Miguel Locks. The correlation of the formations in different areas is shown in figure 4.
The basement on which the Tertiary formations rest consists principally of altered and strongly deformed volcanic rocks, including tuffs that contain marine


10




















C A R


Punta Manzanilla
Punta San Bias


ARCHIPIELAGO lon
del Toro DE BOCAS
VIDEL TORO
Punta Vahiente

PA AMA AREPA


--" 50,JI- PANAMA A ELOS zz 'Volcan de fIA DE, Chmrquf -4 SPunta Chamne Penonom6
O / csARCHIPIELAGO
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S
c-Remedios Aguadulce 0 PER LAS


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LA I ) -20 0 Tonosi La--- Punta Naranjas


0 C F I A


Cabo Tiburdn





an Lorenz



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60 Mikes

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/ N0


FIGURE 1.-RMap of Panam showing principal areas of Tertiary marine sedimentary formations and area covered by plate 1, Base from American Geographical Society's 1:1,000,000 map of Hispanic America.


B B E A N


S


-Y


-4


C I F


B


0
0







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


fossils. The volcanic rocks are intruded by dioritic rocks. This basal complex is probably of Cretaceous age, but so far all that is known about its age, in the region covered by plave 1, is that it is older than middle Eocene. It is much older than MacDoaald's (1913, pl. 4) igneous complex-a map term lie used for volcanic and intrusive rocks of Oligocene and early Miocene age.
The middle and upper Eocene Gatuncillo formation rests with marked unconformity on the basement rocks. It has been identified east of the Canal Zone and in the eastern part of the Zone. Lithologically it is more uniform than the Oligocene and lower Miocene formations.
Formations of known or inferred Oligocene age are of wide extent and very heterogeneous. They are marine and nonmarine, volcanic and nonvolcanic, at least nonvolcanic aside from tuffaceous debris. They represent all of Oligocene time and for the most part are conformable to each other and to the Gatuncillo formation. In the Pacific coastal area, however, the Bohio formation overlaps the Gatuncillo formation and in the northern part of Madden basin the Caimito formation overlaps the Bohio. Except in the Gaillard Cut area, the Oligocene formations are marine or partly marine: the Bohio and Caimito formations. Though the Bohio formation (the older of the two) appears to be for the most part nonmarine, marine strata are found in it at different horizons. Isolated outcrops in the Gatun Lake area, inferred to represent a tongue of marine strata in the lower part of the Bohio formation, contain mollusks considered of eadly Oligocene age and larger Foraminifera assigned to the late Eocene. Smaller Foraminifera of early Oligocene age are found in the basal part of the Bohio in the Quebrancha syncline. In both the Gatun Lake and Pacific coastal areas thin marine deposits in the upper part of the Bohio contain late Oligocene fossils. The Caimito formation overlies the Bohio and is for the most part marine. Late Oligocene fossils, particularly larger Foraminifera, are widespread in the Caimito. In Madden basin, however, the lower part of the formation is late Oligocene and the upper part is early Miocene.
In the Gaillard Cut area the place of the Bobio and Caimito formations apparently is taken by the wholly nonmarine and volcanic Bas Obispo formation and Las Cascadas agglomerate. They are considered Oligocene(?) on the basis of their inferred relations to the Bohio and Caimito formations. The Bas Obispo formation-the older of the two-seems to grade northwestward into the Bohio formation. The Las Cascadas agglomerate is thought to be the equivalent of the lower part, or perhaps all, of the Caimito formation of the Gatun Lake area.


The upper part of the Caimito formation of Madden basin, including the formally named Chilibrillo limestone and Alhajuela sandstone members, consists of marine deposits of early Miocene age. Nonmarine and marine lower Miocene deposits in the Gaillard Cut area are subdivided into relatively thin formations: in ascending order, the Culebra formation (including the Emperador limestone member), the Cucaracha formation, and the Panama' formation (including the La Boca marine member and Pedro Miguel agglomerate mornber). These three formations contain more volcanic material than supposedly equivalent deposits in Madden basin. The marine Culebra formation transgresses northward across the Las Cascadas agglomerate. According to present interpretations, the La Boca marine member of the Panama' formation interfingers with the upper part of the Cucaracha, or overlaps the Cucaracha and Culebra formations and rests on the Bas Obispo. All three formations and some of the lower Miocene of Madden basin are assigned to the upper Oligocene by some paleontologists.
The two Tertiary formations younger than those of early Miocene age are found only in the Gatun Lake and Caribbean coastal areas. These youngest formations are marine and, like the Eocene Gatuncillo formation, are more uniform lithologically than those of Oligocene and early Miocene age. The middle and upper Miocene Gatun formation is famous for its wellpreserved fossils. Though the field relations between the Gatun and Caimito formations are unknown, the two formations evidently are separated by a discontinuity and perhaps by slight discordance. East of the Canal Zone the Gatun overlaps onto the Creteceous(?) basement. The Gatun of the region covered by plate 1 is considered to be middle Miocene. The Gatun at the west end of the outcrop area, about 5G kilometers southwest of Colon, in the western part of the region shown in figure 3, is assigned to the late Miocene.
The lower Pliocene Chiagres sandstone is the youngest of the Tertiary formations. It overlies and partly overlaps the Gatun formation. The thin Toro limestone member lies at the base of the Chagres in the eastern part of the outcrop area.
All the Tertiary formations are somewhat tuffaceous but the oldest and youngest contain the least tuffaceous debris, the Oligocene and lower Miocene the most. Moreover, the Oligocene and lower Miocene formations show a progressive southwestward increase in volcanic and intrusive rocks, until in the southwestern part of the region covered by plate 1 there is nothing but volcanic and intrusive rocks. The change is strikingly shown on plate 1; in fact, more so than would be the case if the map were equally detailed throughout. The volcanic rocks themselves and also the intrusive rocks


12






GEO

are undifferentiated in the southwestern part of the map area. These undifferentiated rocks, however, adjoin a strip along the canal where greater detail is shown than elsewhere on the map.
CRETACEOUS(?) SYSTEM
The oldest rocks in the Canal Zone and nearby, much older than any seen along the canal, are chiefly altered lavas and dioritic rocks. These extrusive and intrusive rocks are briefly described or mentioned under the heading "Igneous rocks.' Altered tuffs and other altered sedimentary rocks are associated with the lavas. None of these rocks, sedimentary or igneous, was studied during the field work and they were observed only casually. They crop out iu the eastern part of the Zone and extensively in Panami east of the Zone, making up the basement on which the Tertiary formations rest. This basement on the borders of Madden basin was designated the volcanic complex by Reeves and Ross (1930, p. 18).
Everywhere the basement forms high, rugged forested uplands and mountains. The composition, structure, and age of these rocks are important aspects of Panamanian geology that remain to be studied. Contrary to the expectation of geologists not familiar with the tropics, the high-gradient streams in the rugged terrain characteristic of the basement offer a wealth of rock outcrops. Moreover, the streams are so numerous that a closely spaced network of outcrops is available.
Strongly deformed altered tuffs were seen at a few localities. Three samples of different grain size, ranging from very fine-grained to very coarse and agglomeratic, were collected on the Transisthmian Highway 2 kilometers east-southeast of the bridge across Rio Gatfin. They were examined by W. S. Burbank, who found them to be moderately to strongly chloritized and carbonatized. The coarse-grained rock contains andesitic andlatiticfragmentsand some devitrified glass. The two samples of finer grain contain angular fragments of feldspar, pyroxene, iron oxides, and quartz. These rocks of finer grain are sheared and fractured, and cut by veinlets of calcite and a colorless mineral, probably a zeolite.
Sedimentary and pyroclastic rocks of the basement complex at the Hyatt manganese prospects near Rio Boquer6n, the southernmost of which is shown at the north edge of the general geologic map (pl. 1), consist of siliceous limestone, quartzite, sheared agglomerate, and fine-grained tuff(?) altered to schist (Simons, in Roberts and Irving, 1957, p. 121, 124).
Though the age of the basement rocks is unkownother than that they are older than the unconformably overlying middle and late Eocene deposits-they probably are Cretaceous, like widespread volcanic and


LOGY 13

associated rocks throughout the Caribbean region (Woodring, 1954, p. 722-725). Late Cretaceous Foraminifera (Globotruncana and Gdmbelina) are reported to have been found in northwestern Panamd, near the Costa Rican border, in siliceous limestone that presumably represents the same major unit as the basement rocks of plate 1. The basement, however, may include rocks older and younger than Cretaceous. The altered tuffs sampled near Rio Gatdn are not the kinds of rocks that would be chosen as being likely to contain fossils. Yet thin sections of the three types sampled show indeterminable Foraminifera and Radiolaria. If further work on the basement rocks is undertaken, it doubtless is only a matter of time until identifiable fossils are found. The siliceous limestones are particularly promising for microscopic fossils.
EOCENE SERIES
GATUNCILLO FORMATION
Formations of Paleocene and early Eocene age are unknown in the central Panama area. They may, however, be represented in the basement complex or by overlapped deposits in the structurally deeper parts of the area. The oldest known Tertiary formation is the Gatuncillo formation, which lies directly on the Cretaceous(?) basement.
The Gatuncillo formation was named by Thompson (1944, p. 12-13) as the Gatuncillo shale. The type region is in the valley of Rio Gatuncillo on the east limb of the Quebrancha syneline. The name Tranquilla shale has priority, but that name was defined inadequately, principally on the basis of foraminiferal samples from a locality in Madden basin later flooded by Madden Dam (Coryell and Embich, 1937, p. 289; for location of Tranquilla see Reeves and Ross, 1930, pl. 5).
The Gatuncillo crops out in the eastern part of the Canal Zone and east of the Zone. It forms rolling lowlands, which stand in contrast to the rugged uplands characteristic of the basement complex. The thickness of the Gatuncillo is estimated to range from 150 to 800 meters. The formation unconformably overlies the Cretaceous(?) basement. In the type region and in other areas wherever the succession is complete, the Gatuncillo is conformably overlain by the Bohio formation. In Madden basin, however, the Bohio is overlapped by the Caimito formation. In the Pacific coastal area the Gatuncillo does not appear between the basement and the Bohio formation, being overlapped by the Bohio. Collections of larger Foraminifera sent to T. W. Vaughan many years ago by A. A. Olsson and R. A. Terry indicate that Eocene deposits reappear farther east in the Pacific coastal area in the valley of Rio Bayano, 45 kilometers east-







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


northeast of the eastern edge of the area shown on plate 1 (Terry, 1956, p. 32).
Though the Gatuncillo consists chiefly of mudstone and siltstone, it includes bentonitic mudstone, sandstone, and limestone, and at the base conglomerate of variable thickness.
STRATIGRAPHY AND LITHOLOGY
Rio Agua Sucia area.-The Rio Agua Suia area lies west of the Quebrancha syneline, between the Azota Caballo and the Agua Sucia faults. Before it was realized that the deposits in the Rio Agua Sucia area are of Eocene age, the name Rio Duque shale was proposed for them (Thompson, 1944, p. 21-23). The area is crossed by the Transisthmian Highway. Cuts along the highway expose mudstone, siltstone, and sandstone of the Gatuncillo formation. Mudstone and siltstone are more prevalent in the southeastern part of the area, sandstone in the northwestern part. The mudstone is more silty than in the Quebrancha syncline; sandstone is more prevalent than in other areas; and northwestward, which also is stratigraphically upward, the sandstone is of coarser grain than in other areas. Sandstone at locality 271 is medium-grained, poorly sorted, and contains much carbonaceous debris. The strata at locality 28 consist of poorly sorted gritty sandstone. The northwestward increase in grain size suggests that the depositional margin of the central Panama area was not far to the north.
So far as observed, limestone is not common. Algalforaminiferal limestone, about 15 meters thick, forms a little hill at locality 25, and foraminiferal limestone crops out at locality 23a.
Quebraecha synclie.-In the type region, on the east flank of the Quebrancha syncline, the maximum thickness of the Gatuncillo formation is estimated to be 800 meters, apparently greater than in other areas. An earlier estimate of 3,Ot feet (900 meters) probably is excessive (WoodrinDg and Thompson, 1949, p. 227). Fine-grained rocks-mudstone and siltstone-make up the bulk of the formation. Limestone, bentonic mudstone, sandstone, and conglomerate are minor constituents. Typical fine-grained rocks are readily accessible on Rio Quebrancha about 100 meters upstream from the Transisthmian Highway bridge (locality 21). The limestones are algal and foraminiferal and most of them have a thickness of less than a meter, such as I The localities at Which fossils were collected are listed on pages 112-130 and, unless otherwise specified in the list, are plotted on the general geologic map (pl. 1).


those off the north side of the Transisthmian Highway 50 meters east of the bridge across Rio Gatuncillo (locality 20) and along the road leading southward from the Transisthmian Highway to Nuevo San Juan (localities 22, 23). On Quebrada Fea (the stream on the east side of Rio Gatuncillo valley 4 kilometers northeast of the Transisthmian Highway bridge across Rio Gatuncillo), however, algal-foraminiferal limestone has a thickness of at least 10 meters. Conglomerate and sandstone at the base of the formation are 'xposed on the Transisthmian Highway. The conglomerate, resting on Cretaceous(?) altered volcanic rocks, has a thickness of 30 to 90 centimeters and is made up of pebbles and cobbles of altered volcanic rock. It is overlain by soft medium- to fine-grained sandstone grading upward into soft silty fine-grained sandstone. The thickness of the sandstone is 6%2 meters.
Madden basin.-The largest outcrop area of the Gatuncillo formation is in the northern and northeastern parts of Madden basin. Much of the outcrop area, however, is flooded by Madden Lake. The Eocene deposits of Madden basin were included in the Bohio formation by Reeves and Ross (1930, p. 17-18), although they are strikingly unlike those of the Bohio. The thickness of the formation is difficult to estimate, but probably is not more than 300 meters.
Limestones are more extensive and individual units of limestone are thicker than in other areas. As elsewhere, algal or algal-foraminiferal limestone is most common, but other kinds of limestone are represented. Algal and algal-foraminiferal limestone in the upper part of the Gatuncillo at locality 14 is fully 30 meters thick. It is separated by sand strata from an overlying algal limestone that reaches a thickness of about 15 meters. Similar algal limestone, also about 15 meters thick, forms the natural bridge (puente natural) on Rio Puente. A cliff on the north side of Rio Puente, 800 meters in a direct line upstream from the natural bridge, exposes almost the same thickness of limestone. Silty somewhat fissile echinoidbearing limestone (plate 4), soft yellowish marly limestone, moderately soft coralliferous limestone, and hard algal limestone, all representing a thickness of 10 meters, are exposed in a partly demolished hill at locality 11. There are numerous other exposures of limestone in Madden basin; in fact, all the fossils from that area were found in limestone. That limestone may occur at the base of the formation is shown by the following section measured on the south side of Rio Pequeni:


14








Section of basal part of Gatuncillo formation on south side of Rio
Pequeni near head of Madden Lake (locality 1)
Gatuncillo formation: Meters
Limestone, thin-bedded nodular-weathering; lowest 1 meter more granular and somewhat sandy.
Scattered angular pieces and few pebbles of basement rocks (diameter of largest 8 centimeters) throughout lower half, more numerous in some layers. Lepidocyclina abundant; many Yaberinella in one layer. Collection (locality 1a) 3 to 4.5
meters above base--_--- ---- 10. 6
Unexposed (possibly sandy or silty strata) _---- 1. 5
Limestone, thin-bedded, in thicker beds than overlying limestone. Contains Lepidocyclina and Yaberinella. Collection (locality 1) 0.5 meter
above base -- ............-----.--------- 1. 5
Unexposed (possibly sandy or silty strata) 1. 5 Limestone, few boulders of altered volcanics at base 5 Basement of altered volcanic rock.

Thickness of section.--.... ---.--... --------_-.. 15. 6

Fine-grained and sandy rocks presumably make up the bulk of the formation. Fine-grained rocks are not readily accessible, but they doubtless could be found by traversing streams. Sandy strata form a treeless area surrounding locality 11 and sandy strata in the upper part of the formation near locality 13 include practically pure quartz sand.
Rio Agua Salud area.-The Rio Agua Salud area is the long, narrow strip of the Gatuncillo formation on the upthrown side of the Chinilla fault, in the eastern part of the Canal Zone. Coring along the alinement for a diversion channel for Rio Chagres-part of the Sea-level Canal project-showed the presence of the Gatuncillo formation in this area, the first record of Eocene deposits in the Canal Zone. R. H. Stewart and T. F. Thompson recognized larger Foraminifera of the Gatuncillo formation in cores from core hole SL84 (locality 29), drilled in 1947, and in float limestone at the core-hole locality. Their age identification was confirmed by W. S. Cole, who described the Foraminifera (Cole, 1949). The three localities in the Rio Agua Salud area are core holes (localities 29-31), wbich started and bottomed iis the Gatuncillo formation. The strata penetrated consist of mudstone, siltstone, silty sandstone, calcareous siltstone, silty limestone, and limestone. The depth of penetration ranged from 30.7 to 54.1 meters.
Rio Frijol area.-The Rio Frijol area includes the outcrop area of the Gatuncillo formation in the drainage


basin of Rio Frijol and the smaller area farther east. The thickness of the formation along Rio Frijol is estimated to be between 300 and 400 meters. The lithologic types are similar to those elsewhere: mudstone, siltstone, sandstone, and thin beds of limestone. Some of the sandstone contains carbonaceous debris. For a discussion of the Gatuncillo formation in the Gatun Lake area seaward from the Rio Frijol area see page 61.
Gamboa area.-A narrow band of Gatuncillo rocks lies in the lowland north of the high ridge north of Gamboa. The strata dip northeastward and appear to be overlain in normal succession by the Bohio formation. If the high ridge is underlain by basement rocks, as shown on plate 1, and if the Gatuncillo is not bounded by faults to the south or north, the thickness of the Gatuncillo is not more than 150 meters. The only outcrop of the Gatuncillo seen in this area consists of calcareous mudstone containing a thin layer of limestone (locality 37).
Rio Casaya area.-Outcrops of fossiliferous rocks of the Gatuncillo formation were found by R. H. Stewart along Quebrada de Oro, a northwestward-flowing tributary of Rio Casaya about 4 kilometers southeast of Gamboa (locality 38). The stream may be recognized by mine-machinery debris and caved adits. Limestone, sandstone, and siltstone of the Gatuncillo formation are intruded by dacite porphyry. These sedimentary rocks are partly silicified. They probably are faulted against the Caimito formation, although no fault is shown on plate 1.
No outcrop areas of the Gatuncillo formation are known southwest of the Rio Casaya area. Though the formation seems to be thinning southwestward, it may extend farther in that direction beneath the Oligocene and lower Miocene strata penetrated by the canal and the undifferentiated volcanic rocks farther southwest.
FOSSILS AND AGE
Soaller Foraminifera.-In most of the areas smaller Foraminifera are abundant in mudstone and siltstone. Coryell and Embich described species collected at Tranquilla, a village on Rio Chagres flooded by Madden Lake, and assigned the fauna to the upper Eocene (Coryell and Embich, 1937). H. H. Renz and P. J. Bermudez kindly identified the following species in five samples:


GEOLOGY


15








1 6


GEOLOGY AND PALEONTOLOGY OF CANAL ZONE Smaller Foraminifera from Gatuncilloformation Smaller Foraminifera from Gatuncillo for nation-Continued
[Identifcations by 11. 0. Renz and P. J. BermndezI [Identifications by HT. 0. Renz and P. J. Berndez] Localities Localities



Q 2 C 0




17 21 24 31 35 17 121 24 31 301


Alabanina sp -_- _-- _-- __---- _Alloomorphina trigona Reuss _---_n-Angulogerina sanjuanensis Coryell and
E m b ich - _- ___ _- _- .. _ _--- _-
sp -----_..- --.--Anomalina pacoraensis Coryell and
E m bich _-- _- _____- _- ___b___---cf. A. alazanensis Nuttall ---sp - -_ -_-_ _-_- _-_- - _- -- _- _-
A nonoalinoides sp ------ ..___..-__-_A stacolus sp -------.-.. ---_ -_ ___-_-Bathysiphon eocenica Cushman and
H an n a - .-_ __- _- _- --_ -_ --_
Bolivina alazanensis Cushman_-----byramensis Cushman --__--_---gracilis Cushman and Applin_--..cf. B. gracilis Cushman and App lin .. .-- _ _- - - _- - .-
jacksonensis Cushman and Applin

cf. B. jacksonensis Cushman and
A pp lin ----------.. -- ------maculata Cushman and Stone -cf. B. maculata Cushman and
S to n e _ _ _ _- __o- _ _._-
malkinae Coryell and Embich
cf. B. ventricosa Galloway and
H er inway-__.. -.... -..
s p - - - - - -

Bulinina alazanensis Cushman-----consanguinea Parker and Berm ddez -- --_ --_-_cf. B. cooperensis Cushman _-.-guayabalensis Cole .-_-----of. B. impendens Parker and Berm ddez - ---- _jacksonensis Cushman.._ ---cf. B. jacksonensis var. cuneata
Cushman_ -_ __--_---_palnerae Parker and Bermnddez_ cf. B. palnerae Parker and Berm ddez -----_ .. --_--_- _-pupoides d'Orbigny ---- --cf. B. pyrula d'Or igny _- __-- --tuxpamensis Co _-_----sp - .._.._---- ___-----------


X
X
X


?


Buliinella sp
Cassidulina crassa d'Orbigny
havanensis Cushman and Bermddez-
subglobosa Brady
sp -----Cassidulinoides sp Ceratobulimina alazanensis Cushman
and HarrisChilostomella mexicana Nuttal
cf. C. ovoidea Reusssp -----Chilostomelloides oviformis (Sherborn
and Chapman)
Chrysalogonium cf. C. asperum Cushman and Stainforth
elongatum Cushman and Jarvis--sp -----Cibicides cocoaensis (Cushman) -----cf. C. concenlricus (Cushman) -- cf. C. cookei Cushman and Garrett
leoni (Bermddez) meicanus Nuttall

perlucidus Nuttall
cf. C. perlucidus Nuttall
cf. C. pseudoungerianus (Cushman)---_
sp -----n.spp -----Clavulinoides cubensis Cushman and
Bermddez
havanensis Cushman and Beroddoz
op-z----------sp _- - - - - - -
Cornuspira olygogyra Hantken of
Cushoan
Cyclammina cf. C. pacifca Bek
sp -----Dentalina of. D. communis d'Orbignyof. D. cooperensis Cushmnan-cf. D. 0mcronata Neugeboren
semilavis Hantken
oP --------------spp -----Discorbis sp


X


X








GEO

Smaller Foraiinifera from Gatuncillo for ation-Continued
[Identifications by 1t. H. Renz and P. T. Bermnadez]

Localities









17 21 24 31 35


Dorothia cylindrica (Nuttall)_----.-- X ---- X
cf. D. nuttalli Cushman -- _- _---- --__ ---_ X _--sp -- ---_____--_-____ ---- x X x X
Ellipsoglandulina labiata (Schwager) __ -- ---- X ---- ---multicostata (Galloway and Morrey) ---__- __-----___- ---- X -Entosolenia cf. E. laevigata (Reuss) _--- X ---- ---- ---cf. E. marginata (Walker and
B oys) -__-_.. -_ --_-_-__ -_ --- -___ X ---- X ---orbignyana (Seguenza)_ -- --- X ---- ----


Eponides jacksonensis Cushman-----of. E. rutteni Cushman and Bermddez --- ------~~----------umbonatus (Reuss)__-- ---var. multisepta Koch
Frondicularia tenuissima Hantken----Gaudryina (Pseudogaudryina) cf. G.
jacksonensis Cushman------------Glandulina sp. Globigerina ciperoensis Bolli---------ouachitaensis Howe and Wallace sp--- --------- ------ ~- ~

Globigerinoides mexicanus (Cushman) _sp--------------- ----- ---Globobulimina hannai Cushman and
Ellisor--taa ~-----------------cf. G. hannai Cushman and Ellisor~ sp------------- ---~~Globorotalia centralis Cushman and
Bermddez ..- ..--Globulina of. G. gibba d'Orbigny-----rotundata (Bornemann)..-----ap ---------------------Gambelina cubensis Palmer
martini (Pjipers) -Guttulina irregularis (d'Orbigny) --Gyroidinoides girardana (Reuss)_---guayabalensis (Cole)_- -__-__soldanii var. octocamerata (Cushman and Hanna)------------sp.-__------------------__


Smaller Foraminifera from Gatuncillo formation-Cotinued
[Identiflcations by H. H. Renz and Pt. Bermdez]

Localities








17 21 24 31 3


Hantkenina alabamensis Cushman----- X ---- X X
suprasuturalis Bronnimann -- __ _-_--__- X X -Haplophragmoides cf. H. dibollensis
Cushman and Applin --_-_-_ ----- -- __- -- X --- _-_-X
Hastigerinella eocanica Nuttall_ _- __- __-- _-- -- --_-_ X -
s p - _ _- - -_ -__ _ _ - ----__ _ x_ _ _

HMglundina elegans (d'Orbigny) ------- ---- X X X X
Karreriella arenasensis Cushman and
B erm ddez __-- _--- ___- ____-- _- _----- X _- - --
chilostoma (Reuss) -mexicana (Nuttall)a ___ --- --_-- _ X
cf. K. mexicana (Nuttall)_ _-_-_-_-_------_ X -- X -sp -- -------------------------- X -----_--- X

Lagena acuticostaa Reussa------------aa -_ --_ -- X X
f. L. hexagona (Williamson)--- X --sp _ _ _ _ _ _ _ _ __- - - - -- - - _ - X
Lagenoglandulina subovaa var. chagresensis Coryell and Embich------ X -------- --- X
Lagenonodosaria cf. L. sigmoidea Coryell and Rivero -- ------ -- -- X -- ---- --- --ap ------------------ -----x --- -Loxostoma dalli (Cushman) ---------- X [---- X --arginttlina cf. abbreviata NeugBor3nm tteduta Ne -ren X ---cf. 31. eximia Neugeboren- ------ X X ---- X -hantken (Bandy) [-..------------- ---- ---- -- X
f. M. subcrassa Schwager---at -- -- X --- --
cf. M. triangularis var. panamensis Coryell and Embich-_------- ---._ ---- X ----sp------------------------- X X X --- X


Marginulinopsis cocoaensis (Cushman) ----- ---- X
ap------------------------ --- --- K -- -Matanzia? sp -----h-------------------------- X
Nodogenerina heterosculpta Berm6dez-- ---- X --- ---- -ap --- ------ -[ -Nodosaria chirana Cushman and
Stone ------------------------- X ---- --
longiscata d'Orbigny------------ X X X X --multilineata (Bornemann - --soluta (Reuss)-------------- ------------- [K
sp --------- --- --- [ -



























N


I


c .pomp o es ( c tean
Moll)----------------------sp-.---------------------Orthomorphina cf. 0. rohri (Cushman
and Stainforth)------------------Osangularia mexicana (Cole) --------sp---------------------------Planularia sp .....- _______Planulina marialana Hadley------suturata Cushman and BermddezPlectina nuttalli Cushman and Stainforth-- -- -- ----- ------ ---Plectofrondicularia cookei Cushman ---morreyae Cushman vaughani Cushman sp - -_-...... -....Pleurostomella alternans Schwager_____cf. P. palmerae Bermddez _----__cf. P. praegerontica Cushman and
Stainforth -- --__-_-Sp. -__.---...---_-..---__Pseudogqandulina laevigata (dOrb ig n y ) .. .. _ - -_ - -_ - --. -- -
cf. P. laevigata (d'Orbigny) -__ovata (Cushman and Applin)----radicula (Linn6)----_----cf. P. radicula (Linn6) -_--_--_--P.-....--------- ----Pullenia cf. P. bulloides (d'Orbigny)-
sp
Pyrgo pseudoinornata Cushman and
Stainforth __...-- _- ._..- -- .---oP--- ---- ----.----- -Quinqueloculina s-----.---------..
Robulus of. R. dicampylus (Franzenau)
terryi Coryell and Embich--.----spP ---------------.-------.
Rotaliatina maxicana Cushman-.--.--


x


x


X X

X

---x
X -


x
x


x


x


ef. AS. hantkeni (C_.UShnan. ----cf. S. latifrons (Brady)
cf. S. schencki Cushman and Hobson - - - - - -

Schenckiella cf. S. petrosa (Cushman
and Bermddez)--------sp -----Sigmoilina tenuis (Czjzek) Sigmomorphina sp Siphogenerina op Siphonina advena Cushman ----tenuicarinata Cushman

Siphonodosaria cf. S. annuoifera (Cushman and Bermddez)
aff. S. curvatura (Cushman)
cf. S. dentaliniformis (Cushman
ard Jarvis) - --..
cf. S. nuttalli (Cushman and
Jarvis) ------_. -. ----- -paucistriata (Galloway and Morrey)
puntensis Coryell and Embich......

recta (Palmer and Bermddez) --- aff. S. subspinosa (Cushmae)-_...
verneuili (d'Orbigny) -...........
var. emaciata (Palmer and
Bermddez)---.--.---sp. ----------------.------ -Siphotextularia op ......-- .-. -Spiroloculina cf. S. texana Cushman
and E llisor___-.- ..._ _--_- ..--- ...sp.---------.-----------Spiroplectammina planulis (Coryell
and Embich) ------- .---- ..----Textularia hockleyensis var. cmalkinae
Coryell and Embich ..
cf. T. recta Cushman...-----....Textularia? sp---- .---- ..- -------


x


x


x

x


x
x


x


x
x


x


x


x


x
x x


x

x


8 GEOLOGY AND PALEONTOLOGY OF CANAL ZONE Smaller Foraminifera from Gatuncillo formation-Continued Smaller Foraminifera from Gatuncillo formation-Continued
[Identifications by H. H. Renz and P. J. Bermndez] [Identifications by H. H. Renz and P. J. Berradez] Localities Localities








it 21 24 31 to 07 21 00 01 50 'onion danoittenoe Hoar and Wattacc. X -- X X X Saracenaria acotauricutaris (Fiohtet
pampitioides (Ftehtet and Mott)_- X ---- -- and Molt)---..--..----..X ---
CD Nd i0i C3h 0d










Smaller Foraminifera from Gatuncillo formation-Continued
[Identifications by H. H. Renz and P. Bermddez] Localities

M Cl C111


15 ra n I
.2 .0 .0
17 21 24 31


Textulariella sp --_ -- ------------ _Triloculina cf. T. globosa (Hanna and
H anna) ----------- ------ _---cf. T. subrotundata (Montagu) .--I'D ----------------------------Uvigerina adelinensis Palmer and
Bermddez..--------------------of. U. atwilli Cushman and Simonson ------------------------cf. U. chirana Cushman and Stonecurta Cushman and Jarvis------gardnerae var. nuttalliana Howe
and Wallace

opissicosaoa Cushinan and Jarvis- opinolosa Coryell and Embich_...
cf. U. spinulosa Coryell and Embich ----_ _- - _- ---- _sp _-..---.---.----

Vaginulinopsis mexicanus (Nuttall) -
of. V. mexicanus (Nuttall)-.-sp -------- ---- .----.. -_Valvulineria cushmani Coryell and Embich ------------------------gasparensis Bermddez----------Virgulina cf. V. danvillensis Howe and Wallace.-..-. ---.... _.
of. V. dibollensis Cushman and
Applin---------------------cf. V. advena Cushman
pachyheilus Hadley-_
sp -.----_-..----. .- --


I I I I


of the pelagic species-with assemblages from other regions where the stratigraphic position and age are fairly well established. It should be mentioned, however, that the boundary between the lower part of the upper Eocene and the upper part of the middle Eocene, on the basis of smaller Foraminifera, is uncertain throughout the Caribbean region.
Two main upper Eocene faunal units are represented: an earlier (localities 24, 31, 17, and 35) and a later (locality 21). The earlier unit itself suggests two minor units: the older represented by localities 24 and 31, the younger by localities 17 and 35.
The fauras from localities 24, 31, 17, and 35 are characterized by the occurrence of Bulimina jacksonensis (or a related form), Globorotalia centralis, and Hantkenina alabamensis or H. suprasuturalis. They show distinct affinities with faunas of the Jackson group of southeastern United States, the Jicotea member of the Jabaco formation and the San Luis formation of Cuba (Bermddez, 1950, p. 249-258), the Pauji formation of Venezuela (Nuttall, 1935), and the lower part of the Mount Moriah forniation and the Hospital Hill marl in the San Fernando group of Trinidad (Cushman and Renz, 1948).
The fauna from locality 21 has upper Eocene and lower Oligocene affinities. It lacks Globorotalia centralis and Hantkenina. The presence of a form related to Bulimina jacksonensis, however, indicates a late Eocene age. This fauna suggests relationship with that of the Consuelo formation of Cuba (Bermddez, 1950, p. 258-262).

Larger Foraminifera.-The first Eocene fossils from Panam6 were recorded in 1891, when Douvill wrote that calcareous algae and heterostegine and orbitoid Foraminifera were found in limestone at San Juan in the upper Chagres valley (DouvillS, 1891, p. 498, 499). He thought the fossils to be of Oligocene age. By the time his second note on the age of the beds along and near the canal was published, he recognized that the orbitoid found at San Juan represents the genus Lepidocyclina (DouvillS, 1898, p. 598-599), later named L. chaperi as a tribute to the collector, an engineer of the first French canal company (Lemoine and R. DouvillS, 1904, p. 14). In a still later publication DouvillS reiterated the Oligocene age, as he was not then aware of the presence of Lepidocyclina in the Eocene (DouvillS, 1915, p. 129-130). At that time, however, lie recorded the occurrence of a stellate discocyclinid ("Asterodiscus") in association with Lepidocyclina in another sample of limestone from the upper Ciagres valley. Vaughan (1919b, p. 549, table opposite p. 595) left these strata in the Oligocene, despite Cushman's suggestion (in a footnote to Vaughan's table) that they should be referred to the upper Eocene. San Juan was located on Rio Pequeni and is submerged by Madden Lake. (For location see Reeves and Ross, 1930, pl. 5.) E. R. Lloyd collected at San Juan in 1919 before Madden Dam was built (locality 3 of present report). When this collection was sent to Vaughan in 1926, he found that at its type locality Lepidocyclino chaperi is associated with late Eocene species (Vaughan, 1926).


X


Barring unknown structural complications and overlaps, localities 24 and 31 represent the lower third of the Gatuncillo formation, localities 17 and 35 the middle third, and locality 21 the upper third. The following comments concerning the five samples were prepared by Messrs. Renz and Bermudez:

A considerable number of species and varieties are unidentified, either because they are undescribed or because comparative material was not available.
The smaller Foramisifera in the five samples represent various levels in the upper Eocene. The age determinations are based on a correlation of the faunas-with special emphasis on some


GEOLOGY


19







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


Larger Foramiaifera are the most abundant and widespread fossils in limestone and calcareous mudstone of the Gatuncillo formation. Loose specimens weathered out of both kinds of rock are most suitable for identification, as oriented thin sections can be prepared. At many localities these fossils weather out of hard limestone because they are silicified or partly silicified, whereas the limestone is not silicified. Plate 3 shows elective silicification and iron staining in a slab of limestone collected at locality 14. At locality 13 specimens of a small Lepidocyclina, probably L. pustulosa, are completely silicified and covered with beekite excrescences, producing fantastic effects. Though no larger Foraminifera from the Rio Casaya area appear in the


table of identified species, they were found in the area. The partly silicified limestone that yielded mollusks under acid treatment also yielded many specimens which probably are Lepidocyclina pustulosa. They are hollow, however, and therefore indeterminable. Float limestone in the Rio Casaya area contains somewhat silicified specimens of a saddle-shaped Lepidocyclina, probably L. chaperi.
Samples of larger Foraminifera were collected at 27 localities. Those from 15 localities were selected, on a basis of favorable preservation and geographic and stratigraphic range, for study by W. S. Cole, whose report was published in 1953 (Cole, 1952 [1953]). His identifications are as follows:


Larger Foramiinifera from Gatuncillo formation
[Cole, 1952 (1953), p. 4]


Yaberinella jamaicensis Vaughan Operculinoides floridensis (Heilprin) __
jacksonensis (Gravell and Hanna)
noodybranchensis (Gravell and Hanna)
ocalanus (Cushman) _--- -_vaughani (Cushm an) _-_---_-_-_ ---_-_ ---_-_Nusmmnulites 2 strialoreticulatus L. Rutten Heterostegina ocalana Cushman ___-__ Fabiania cubensis (Cushman and Bermddez) Helicostegina soldadensis (Grimsdale) ----_-_ -----_

Lepidocyclina (Lepidocyclina) montgomeriensis Cole
(Pliolepidina) gubernacula Cole --_-__
macdonaldi Cushman.__-_--- pustulosa H1. D ouvil .6 ..- _-_- __- __pustulosa tobleri H. Douvil6 __ ___- _____(Nephrolepidina) chaperi Lemoine and R Douvi6-


Helicolepidina spiralis Tobler Asterocyclina georgiana (Cushman)
mariannensis (Cushman) --minima (Cushman)___-_----Pseudophraginia (Proporocyclina) flintensis
man)_ --------


(Cush-


Madden basin


1 2 1 4 110


Rfo Rfo GainQuebrancha synclina Rfo Agua Agua Frijol boa sucia area salud area area
Saia a r s,, e a

11 19 22 23 26 27a 28 29 33 37




- ---- -- ------- - - --- - X - --


- -X --- X
--- - X
X -_ X -x X - X
- --- -x- --- --S----x-- ------- ----
- ---- X
X x x x -_- --- X X ---- x
x X X ---- -_-- X X X
-- X X --- --- - -- -- -- X - -- X
X X X X -----x X - X x X

-X----- X --X X ---
x X X ---- X ---- X ------ -- ---- --- X ---- ---___ _- - X X x ----


I The locality numbers in Cole's publication are field numbers. For correlation with report numbers of present report see p. 112-116.
2 Cited by Colo as Camerina.


2()









Corals from Gatuncillo formation
[Identifications by J. I. Wells


Lepidocyclina pustulosa, L. macdonaldi, and L. chaperi are abundant and widespread. Discocyclinids (Asterocyclina and Pseudophragmina) were collected at 7 of the 15 localities, Helicolepidina spiralis at 6 localities, Fabiania cubensis at 6, Helicostegina soldadensis at only one. Yaberinella jamaicensis was found in the basal part of the formation (localities 1, 1a), associated with Fbiania cubensis. Nummulites striatoreticulatus is a relatively large nummulite for an American species. Operculinoides is extraordinarily abundant at locality 10.
According to Cole (1952 [1953], p. 4-5), the larger Foraminifera of the Gatuncillo formation are dominated by species characteristic of the upper Eocene rocks of Trinidad and Florida. He also pointed out that two of the species (Yaberinella jamaicensis and Fabiania cubensis) are recorded only from the middle Eocene, but that there are good grounds for considering that the former ranges upward into upper Eocene in Jamaica and the latter into upper Eocene in Cuba.
Corals.-Corals are fairly common in limestone, for the most part hard limestone that yields only random sections. Specimens that weathered out of softer marly limestone and calcareous mudstone were collected at five localities. Such fossils, which generally are poorly preserved, were found to be abundant only at locality 11, where slabs of limestone from a partly demolished hill are disintegrating. The collections were examined by J. W. Wells, who identified the following species:


Heliopora sp - Astrocoenia incrustans Duncan Astreopora n. sp Diploastrea n. sp. aff. D. crasso ellata
(Duncan).-- -.Goniopora aff. G. taberi Wells Esriteo (Synaroes) a. sp------Favia of. F. weisbordi Wells Colpophyllia sp.-- Antillia cf. A. hadleyi Wells Millepora aff. M. alcicornis Linn6-----


Localities

Rio
Madden Aga
basin Oaoia
area

8 1 12 16 26

x------ ---xx
-----------X

x

?x------x --------x
x ---x- ------


Wells reports that the new species of Diploastrea is closely allied to the widespread late Oligocene D. crassolamellata and that the fossils from locality 11 constitute the first record of a pre-Pleistocene alcicornislike Millepora in America. He points out that most of the other species show close relationship to upper Eocene Cuban corals and a less marked relationship to middle Eocene corals from St. Bartholomew.


Mollusks froom Gatuncillo formation (Neritidae to Turritellidae)


Velates perverse (Gmoelin), subsp.? Hannatoma? cf. H-. emendorferi OlssonXenophora sp__--- --- ---__Hipponix sp ----------------------Calyptraea cf. C. aperta (Solander) Polinices? sp -------Neverita? sp -------Sinum sp_ -------Anarellina? sp -----Pachycrommiun, solenaeun?, Woodring, n. sp Turritella cf. T. carinata Lea
ef. T. samanensis Olsson--. .
sp. . . . .


6 7 9 11 12 16 32 X X X X --------x ---- x- ---- x --- -_- X ---

___- X X X X I- -


Madden basin Rfo Frijol Casaarea ya area


34 1 38


GEOLOGY


21







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


Mollusks.-A few microscopic mollusks were recovered from foraminiferal mudstone and siltstone. Molds of mollusks weather out of limestones in Madden basin. The largest number of species represented by such molds was found at localities 11 and 12. Somewhat calcareous sandstone in the Rio Frijol area contains a few species. The best preservation is shown by silicified fossils collected in the Rio Casaya area (locality 38). These silicified fossils are casts composed of granular silica. They occur in partly silicified limestone and therefore can be extracted by treatment with acid.
The species listed on p. 21 are represented in the families covered by Chapter A of the present report.
The mollusks of the Gatuncillo formation include species of Tethyan affinities, an example of which is Velates perversus. Ilannatoma is an American genus, found in the Eocene of Perd, Colombia, and Venezuela, and in the Oligocene of Perd. It is not certain, however, that Hannatoma occurs in the Gatuncillo formation, as the aperture and growth line of the species identified as Hannatoma? cf. H. emendorferi is unknown. Turritella cf. T. carinata, and other species from the Rio Casaya area not included in the preceding list, indicate a middle Eocene age, but the bulk of the fauna suggests late Eocene.
Echinoids.-Echinoids collected at locality 11 were identified by C. W. Cooke (1948) as Cubanaster acuai, Weisbordella dalli, W. cubae, Schizaster armiger, and Eupatagus clevei. Cubanaster acunai is very abundant in slabs of silty limestone that are strewn about at locality 11 (pl. 4). Incomplete remains of Eupatagus were seen at other places in the southern part of Madden basin. According to Cooke, four of the five species at locality 11 are found in the upper Eocene Ocala limestone of Florida, two in the upper Eocene of Cuba, and one in the middle Eocene of St. Bartholomew.
Age.-The Gatuncillo formation is considered to be of middle and late Eocene age. The faunal evidence consistently indicates that the greater part of the formation is late Eocene. Contrary to a former opinion (Woodring and Thompson, 1949, p. 228), the formation, perhaps only a small part of it, evidently includes middle Eocene, at least in Madden basin and the Rio Casaya area. Yaberinella jamaicensis was found in two collections at the very base of the formation, but not in other collections. Though that species occurs in both middle and upper Eocene in Jamaica, its apparently more closely restricted range in PanamA, suggests that the basal part of the Gatuncillo is middle Eocene. Unfortunately no other collections of larger

Durham's relassiication ID riaey, y. ., A new family of clypesltroid et oloids: Jour. Paleontology, v. 28, p. 677-684, 3 figs., 1954).


Foraminifera from the basal part of the formation are now available. The collection of mollusks from the Rio Casaya area includes species of middle Eocene affinities, such as Turritella cf. T. carinata, which are not represented in other collections. Stratigraphic control, however, is completely lacking in the Rio Casaya area.
EOCENE 01R OLIGOCENE SERIES MARINE MEMBER OF BOHIO(?) FORMATION
Marine strata of early Tertiary age in the Gatun Lake area are tentatively designated the marine member of the Bohio(?) formation, pending further data on their stratigraphic relations. They are thought to represent a marine tongue, or tongues, in the lower part of the essentially nonmarine Bohio formation, which is described on pages 24-28. That interpretation, however, is a matter of inference. It is adopted principally because in one of the outcrop areas the strata include rocks similar to those of the Bohio formation.
Whatever the stratigraphic relations of the unnamed strata may be, a separate formation name may eventually be preferred for them. As a matter of fact, a name was casually used for them many years ago-a name incorrect in orthography and no longer suitable: Vamos a Vamos beds or Vamos a Vamos formation (Hill, 1898, p. 179, 205).
Though the thickness and extent of this unit are unknown, the thickness probably is at least 100 meters.

STRATIGRAPHY AND LITHOLOGY
Vamos Vamos.-The unnamed marine strata were first observed near a now submerged village on Rio Chagres that had the intriguing name Vamos Vamos. The approximate position of the fossiliferous strata is shown as locality 40 on plate 1. Though the name Vamos Vamos suggests American slang, my colleague G. E. Lewis informs me that "vamos" is a colloquial equivalent of the more elegant "viimonos" and that reiteration for emphasis is common in many languages. The name appears on Garella's 1:200,000 map, prepared in 1844 and published in 1845 (Garella, 1845). Hill had his own hybrid version of the name: Vamos a Vamos (Hill, 1898, p. 179), gallicized to Vamos a Vamos by MacDonald (1919, p. 542).
The strata described as those at Vamos Vamos actually were exposed in a cut on the southwest side of the French Canal, about 2 kilometers northwest of the place where the canal joined Rio Chagres just upstream from the village of Vamos Vamos. (See map, pl. 1, accompanying publication cited under Bertrand and Ziircher, 1899.) These fossiliferous strata were first mentioned by Chaper (1890, p. 7) and were described by Hill (1898, p. 179-180), Howe (1907, p.


22









Section of marine member of Bohio(?) formation on north coast of Trinidad Island


113; 1908, p. 219), and MacDonald (1919, p. 542). According to these descriptions, the strata dipped toward the northwest and consisted of dark tuffaceous silty sandstone, containing practically black calcareous concretions, and small-pebble conglomerate. Fossils were found in the calcareous concretions and also in the sandstone. MacDonald reported a thickness ol 95 feet (29 meters) at locality 40.
Hill thought the strata at Vamos Vamos to be younger than the foraminiferal marl exposed farther east (Hill, 1898, p. 179), and so did Bertrand and Zircher (1899, p. 88). (The foraminiferal marl, now submerged, is presumed to be part of the Caimito formation.) Howe concluded that the coarse conglomerate and volcanic breccia at Bohio, still farther east, and the strata of finer grain at Vamos Vamos represent different faces of the same formation: the Bohio formation (Howe, 1908, p. 221). MacDonald and Vaughan assigned the strata at Vamos Vamos to the Gatun formation (MacDonald, 1919, p. 542). Though little data on the structure and stratigraphy of the marine member of the Bohio(?) formation are now available, that unit seems to be exposed on an anticline, as suggested on plate 1.
Palenquilla Point.-When Mr. Thompson was reminded of the record of dark fossiliferous calcareous concretions at Vamos Vamos, he remembered that he had seen such concretions near Palenquilla Point, which is close to the submerged Vamos Vamos locality. Tuffaceous siltstone, tuffaceous mediumn- and coarsegrained sandstone, and lenses of conglomerate made up of basaltic pebbles, cobbles, and boulders are exposed at scattered localities on the east side of the peninsula ending at Palenquilla Point. The coarse basaltic fragments generally have a maximum diameter of 10 centimeters, exceptionally 30 centimeters. Loose dark fossiliferous calcareous concretions were found at the edge of Gatun Lake at locality 41 and in place in medium-grained sandstone halfway between that locality and Palenquilla Point. At other places mediumgrained sandstone contains molds of mollusks. The basaltic conglomerate suggests the Bohio formation. Whether these marine strata will be found in an extensive area south and southwest of Palinquilla Point, as suggested on plate 1, remains to be determined.
Trinidad Island.-The same stratigraphic unit forms Trinidad Island. The following section is exposed on the north coast of the island:


Siltstone, sandy. Locality 42c, 4.5 meters above base-.. Sandstone, ledge-forming, silty, medium-grained, calcareous,
containing few pebbles, few worn small heads of calcareous algae, and worn shell tips of Turritella.
Locality 42b -- - - - - - - -
Siltstone, sandy. Locality 42; locality 42a represents a
thin calcareous layer ----_ --- -_--- -- -----T hickness of section ------ _---- _--- _-_-_-.---


Meters
6


3 10


FOSSILS AND ACE
Larger Foraminifera.-No Foraminifera of any kind are in the collections from Vamos Vamos and none were observed in the exposures near Palenquilla Point. The following larger Foraminifera were identified by Cole in two collections from Trinidad Island:

Larger Foraminifera from marine member of Bohio(?) formation, Trinidad Island


[Cole, 192 (193), p.51

Operculinoides jacksonensis (Gravell and Hana)....
.ugteri Vaughan and Cole ----.------trinitatensis (Nuttall)..- .- ..---.-.. -------Nummulites I striatoreticulatus (L. Rutten) Fabiania cubensis (Cushman and Bermddez) Lepidocyclina (Pliolepidina) macdonaldi Cushman(Pliolepidina) pustulosa H. Douvilli-..
pustulosa tobleri H. Douvill6-.----I Cited by Cole as Camerina.


Lecalttites
42 420 X X X X X X


Cole pointed out that all the larger Foraminifera collected at Trinidad Island are found elsewhere in deposits of late Eocene age; in fact, all except two (Operculinoides kugleri and 0. trinitatensis) are found in the Gatuncillo formation. Moreover two (Fabiana cubensis and Lepidocyclina pustulosa) occur in the middle Eocene, but none in the early Oligocene.
Mollusks.-A collection of mollusks from Vamos Vamos was forwarded to the U. S. National Museum by Alexander Agassiz in 1891. Other collections were made by Hill and by Vaughan and MacDonald. All these collections presumably represent the same general locality. For some reason Hill sent in three lots that have different field numbers. Dall used specimens from the Agassiz and Hill collections to describe four species he named Glyptostyla panamensis, Mactra (Mactrella?) dariensis, Cardiue (Fragum) gatunense, and Pitaria (Lamelliconcha) hilli in his monumental


GEOLOGY


23







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


Tertiary Fauna of Florida (Dall, 1890-1903, p. 233, tematic descriptions of chapter A of the present report. 895, 1100, 1268). The collections from localities 41a Species in the families covered by chapter A of the and 41b were received too late to be included in the sys- present report are tabulated below.

Mollusks from marine member of Bohio(?) formation (Phasianedidae to Turritellidae)


Tricolia calypta Woodring, n. sp
Calyptraea sp -Natica (Natica?) sp
Tectonatica sp
Polinices? sp
Neverita? sp

Neverita (Glossaulax) bolivarensis tapina Woodring, n. subsp Sinum sp
Globularia (Ampulella) sp (Ampulella?) nana Woodring, n. sp Pachycrommium? proinum Woodring, n. sp Turritella adela Woodring, n. sp
cf. T. caleta Olsson


The mollusks of the marine member of the Bobio(?) formation are unlike those of the Gatuncillo formation. Tricolia calypta and the unnamed Tectonatica are the earliest known American species of genera that appear in the Paleocene and Eocene, respectively, of Europe. Neverita bolivarensis tapina is a subspecies of a late Eocene Colombian species. Pachycrommium? proinum, the otser globularines, and Turritella adela also have Eocene affinities. Turritella cf. T. caleta appears to be allied to the Oligocene Peruvian T. caleta.
Age.-In view of their stratigraphic range elsewhere, the eight forms of larger Foraminifera point to a late Eocene age (Cole, 1952 [1953], p. 5-6). Had these fossils been found only in the sandstone that contains pebbles, worn small heads of calcareous algae, and worn shell tips of Turritella (locality 42b), the possibility of reworking might be considered, despite the lack of any other evidence for reworkig. Five of them, however, were found also in siltstone (locality 42). So far no early Oligoceie fauna of larger Foraminifera in the Caribbean region has been described although larger Foramnifera of that age quite certainly are represented in the White Limestone of Jamaica, in similar limestones iii Haiti ans thi Doniiiican Republic,, and in Cuba.
Dall itiformed ]ill that the Vaios Vanos mollusks are Eocene (Ihill, 1898, i. 271, 273). Some of the species found there and at the other localities have Eocense affiniities, but others liave later affinities (Woodriig and Thompson, 1949, p. 231). The latter affinities


Vanos vamos 40 40a 40b 40d


Localities

Palenquilla Point 40e 41 41a I4b


y


Trinidad 42 142c


X


and, above all, the Pbsence of typical Eocene genera are thought to outweigh the Eocene affinities and to indicate an early Oligocene age. That age, however, is not based on faunal similarity to the early Oligocene of western Europe or southeastern United States. The most marked faunial similarity is with the late Eocene of Colombia and the late Eocene and early Oligocene of Perd.
Pending resolution of the apparently conflicting testimony of the larger Foraminifera and mollusks, a late Eocene or early Oligocene age is assigned to the marine member of the Bohio(?) formation.
OLIGOCENE SERIES
BOHIO FORMATION
The Bohio formation proper, excluding the doubtful marine member just described, has fairly uniform lithologic features. It is characterized by the preponderance of poorly sorted debris, mostly basaltic: very coarse debris iii the form of boulders and cobbles, and finer debris forming beds of sandstone, or more properly graywacke, and the matrix of conglomerate. The debris evidently came principally from the south and southwest. Boulder conglomerate is the dominant type of rock in the Gatun Lake area, the southern part of Madden basin, and the Pacific coastal area. In the Quebraiiclia sysenline conglomerate is replaced by graywacke grit. In the Gatun Lake area the formation apparently grades southeastward into agglomerate of the Bas Obispo formation.


24






GEO

The poorly sorted conglomerate and the poorly sorted graywacke contain no marine fossils and seem to be nonmarine. Marine fossils are found in thin units in the upper part of the formation, in algal limestone and in both poorly sorted and fairly well sorted subgraywacke. If the tentatively designated marine member of the Bohio(?) formation is indeed the equivalent of the lower part of the Bohio, it represents a northwestward replacement of nonmarine conglomerate by marine sandstone, siltstone, and conglomerate.
Hill named the Bohio formation, but used the spelling Bujio (Hill, 1898, p. 183). The name was derived from Boho or Bohio Soldado, a village on the Panama Railroad located on a bluff overlooking Rio Chagres and now under the waters of Gatun Lake north of Barro Colorado Island. In Spanish orthography the name, anglicized in the Canal Zone, is Bohio. Though the little islands north of Barro Colorado Island are closer to the location of the village, the Bohio Peninsula may be considered the type region.
In his description of outcrops Hill casually used many names that have the form of formal stratigraphic names. His expression "Bujio formation" evidently was intended to mean no more than "the formation at "Bujio." Four of his names-Bujio (Bohio) formation, Culebra clays (altered to Culebra formation), Empire limestone (altered to Emperador limestone member of Culebra formation), and Panama formation-have been preserved.
In complete sections the Bohio formation overlies the Gatuncillo formation. So far as known the two formations are conformable, except in the Pacific coastal area, where the Bohio overlaps the Gatuncillo and rests on basement rocks. The thickness of the Bohio ranges from about 75 meters to perhaps as much as 450 meters.

STRATIGRAPHY AND LITHOLOGY

Gatun Lake area.-Boulder conglomerate is the most characteristic rock type of the Bohio formation in the Gatun Lake area. As shown on plate 5, the conglomerate is a rude assortment of boulders, cobbles, and pebbles. Boulders predominate and reach a diameter of 2 meters. Basalt is by far the dominant rock in the coarse constituents. In general the coarse constituents are better rounded in the northwestern part of the outcrop area, including Barro Colorado Island, where the view reproduced as plate 5 was taken. Conglomerate like that shown on plate 5 borders the launch channel between the two small islands just northwest of the first peninsula on Barro Colorado Island west of Salud Point (Orchid Island and de Lesseps Island, not labelled on plate 1). This channel is the site of the excavation


LOGY 25

for the French locks near the village of Bohlo, mentioned in early descriptions of the Bohio formation.
The poorly sorted coarse-grained matrix of the eonglomerate and similar graywacke forming separate beds is made up chiefly of angular grains of basalt in a clay-like binder. On Barro Colorado Island carbonaceous debris is common in medium- to coarsegrained subgraywacke containing scattered pebbles, generally poorly rounded Marine fossils were found in such sandstone in the upper part of the formation on Barro Colorado Island at locality 42g and 42i. They also were found at locality 42d in medium-grained subgraywacke that is better sorted and has little carbonaceous debris. The fossiliferous sandstone at locality 42d contains somewhat calcareous irregular lumps.
Though conglomerate and sandstone predominate, the formation includes tuffaceous siltstone.
The Bohio formation and Bas Obispo formation appear to intertongue. Both Hill and Howe described agglomerate (volcanic breccia of their terminology) exposed in a quarry at Bohio (Hill, 1898, p. 183; Howe, 1907, p. 112; Howe, 1908, p. 216-217), and Howe described subsurface evidence indicating equivalence of agglomerate and conglomerate (1908, p. 217-218). According to Howe, between Darien and Gamboa a few patches of conglomerate could be seen overlying agglomerate before the flooding of Gatun Lake (1908, p. 215, "in the neighborhood of Mamei, Gorgona, and Matachin"). According to Jones, in the same region conglomerate and sandstone of the Bohio formation grade into agglomerate of the Bas Obispo (1950, p. 899-900).
MacDonald (1913, p. 568) estimated the thickness of the Bohio in the Gatun Lake area to be almost 1,000 feet (300 meters).
Quebrancha syncline.-The Bohio formation in the Quebrancha syncline consists of a graywacke grit member and an overlying volcanic member. Both members have been described by Thompson (1944, p. 13-17). The grit member is made up of poorly sorted coarse, angular grains and scattered pebbles of basalt and thin lenses of conglomerate, in which basalt predominates. The pebbles have an observed maximum diameter of 10 centimeters. In other words, the graywacke grit closely resembles conglomerate in the Gatun Lake area, but has a much finer texture. Like the conglomerate, the grit appears to be nonmarine. Thin marine siltstone, however, was fonnd in the Basal part of the member. The maximum thickness of the member is estimated to be 450 meters.
The volcanic member has a thickness of 30 meters. It consists, in ascending order, of porphyritic basalt (18 meters), agglomerate (9 meters), and greenish waxy







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


bentonitic clay (3 meters). Spheroidal exfoliated masses, which weather out of the basalt and are very durable, were found by Thompson to be useful guides in mapping. This thin volcanic member evidently is a product of the eruptions that produced the Bas Obispo formation and the Las Cascades agglomerate. Study of the volcanic rocks may yield clues as to whether the volcanic member is the equivalent of part of the Bas Obispo or of part of the Las Cascadas.
Madden basin.-The Bohio formation has been recognized only in the southeastern part of Madden basin. The outcrop area in the basin extends southeastward across the continental divide and joins the Pacific coastal area. As in the Pacific coastal area, the formation consists chiefly of poorly sorted massive conglomerate. The estimated maximum thickness is 200 meters. 'PTe absence of the Bohio in the northern part of Madden basin is attributed to overlap by the Caimito formation.
Pacific coastal area.-In the Pacific coastal area the Bohio formation overlaps the Gatuncillo formation and lies directly on basement rocks. The Bohio thins abruptly eastward. On the west side of Rio Cabra, where the formation rests on coarse-grained diorite, the thickness is not more than 75 meters. The outcrop in the western part of the area is very wide because the grade of the slope south of the continental divide is almost the same as the dip of the formation. Cuts along the Transisthmian Highway expose massive poorly sorted conglomerate (pl. 6) and poorly sorted graywacke. Basaltic debris predominates along the highway, but the proportion of basalt decreases eastward. Thin lenses of algal limestone are interbedded with conglomerate in the upper part of the formation at localities 43-45. At locality 44 the limestone has an exposed thickness of 6o centimeters, the greatest observed thickness.

FOSSILS AND AGE

The bulk of the Bohio formation evidently is nonmarine, as sugested by Howe (1907, p. 112-113) and MacDonald (1915, p. 20). Silicified wood is recorded from the formation in the Bohio Pennisula (Berry, 1918, p. 32). Marine fossils, however, establish the presence of marine strata in at least the basal and upper parts of the formation.
Smaller Foraminifera.-Sandy siltstone in the basal part of the graywacke grit tnember of the Bohio at, locality 39, in the Qetebrancia syncline, yielded the following smaller Foraminifera, identified by H. H. Renz and P. J. Bermddez:


Smaller Foraminifera from basal part of graywacke grit member of
Bohioformation at locality 39 in Quebrancha syncline
[Identifications by H. H. Renz and P. J. Bermddez]
Alabamina cf. A. scitula Brady Ammospirata mexicana (Cushman) Angulogerina sp. Astacolus nuttalli (Todd and Kniker)
sp.
Bathysiphon eocenica Cushman and Hanna Bolivina alazanensis Cushman
byramensis Cushman
cf. B. gracilis Cushman and Applin
plicatella var. mera Cushman and Ponton
rhomboidalis (Millett)
tectiformis Cushman
sp.
Bulimina alazanensis Cushman Cassidulina subglobosa Brady Chrysalogonium asperum Cushman and Stainforth
Sp.
Cibicides mexicanus Nuttall
perlucidus Nuttall
spp.
Ctavutinoides cubensis Cushman and Bermddez Cyclammina cf. C. deformis Guppy Dentalina alazanensis (Nuttall)
cf. D. mucronata Neugeboren
semilaevis Hantken
Sp.
Discobis araucana (d'Orbigny) of Nuttatt Epenids umbenetua var. multisepte Koch Gaudryina (Pseudogaudryina) alazanensis Chusman Glandulina sp.
Globigerina ciperoensis Bolli
ouachitaensis Howe and Wallace
Sp.
Gfimbelina cubensis Palmer Guttulina byramensis (Cushman)
sp.
Gyroidinoides cf. G. girardana (Reuss) Karreriella mexicana (Nuttall) Lagena striate (d'Orbigny) Marginslina pseudohirsuta Nuttall
similis d'Orbigny
Nodogenerina cf. N. havanensis Cushman and Bermddez
Sp.
Nodosaria longiscata d'Orbigny
multilineata Bornemann
obliqua (Lcin6)
cf. N. pyrula d'Orbigny
cf. N. soluta (Reuss)
Sp.
Nonion cf. N. grateloupi (d'Orbigny)
pompilioides (Fichtel and Moll) Osangularia mexicana (Cole) Planularia sp.
Planulina marialane Hadley
cf. P. Weetrstorfi (Schwager)
Plectina nuttalli Cushman and Stainforth Plectofrondicularia alazanensis Cushman
meicana (Cushman)
vaughani Cushman


26







GEOLOGY


Pleurostomella alterans Schwager
bierigi Palmer and Bermddez
ef. P. naranjoensis Cushman and Bermddez Pseudoglandulina conica (Neugeboren)
sp.
Pullenia cf. P. quinqueloba (Reuss) Quinqueloculina ef. Q. maculata Galloway and Heminway Robulus ef. R. alazanensis (Cushman)
artirolatus var. lexanus (Cushman and Applin)
iotus (Cushman)
sp.
Schenckiella sp.
Sigmomorphina ef. S. trinitatensis Cushman and Ozawa Siphonina tenuicarinata Cushman Siphonodosaria nuttalli var. gracillima (Cushman and Jarvis)
sp.
Spiroloculine texana Cushman and Ellisor Uvigerina rf. U. adelinensis Palmer and Bermddez
chirana Cushman and Stone
gardnerae var. nuttalliana Howe and Wallace
spinicostata Cushman and Jarvis
sp.
Vaginulina sp.
Vaginulinopsis alazanensis (Nuttall) Virgulina ef. V. dibollensis Cushman and Applin Vulvulina pachyheilus Hadley
Messrs. Renz and Bermudez prepared the following comments concerning these fossils:
The Foraminifera collected at locality 39 are of early Oligocene age. They have distinct affinities with the early Oligocene faunas of the Alazdn formation (or Huasteca formation) of the Tampico region in Mexico (Nuttall, 1932), the Tinguaro formation (or Finca Adeline mar!) of Cuba (Bermddez, 1950, p. 264-270), and Zone I in the lower part of the Cipero formation of Trinidad (Cushman and Stainforth, 1945).
Larger Foraminfera.-The upper part of the Bohio on Barro Colorado Island yielded Heterostegina antillea, Archaias compressus, Lepidocyclina canellei, L. giraudi, L. waylandvaeghani, L. vaaghani, Miogypsina antillea, and M. gunteri (Cole, 1957). Cole identified the following species, which were collected at localities 43 and 45 in the upper part of the formation in the Pacific Coastal area:

Larger Foraminifera from upper part of Bohioformation in Pacific coastal area.
[Cole, 1952 (1953), p. 6] Localitie

Heterostegina antillea Cushman-_---------.------ X X
Lepidocyclina (Lepidocyclina) parvula Cushman_-__-- X --waylandvaughani Cole ------ -- X
yurnagunensis Cushman----------------- X -~yurnagunensis morganopsis Vaughan---------- X X
(Nephrolepidina) vaugtani Cushman------------ -_ X
(Eulepidina) favosa Cushman_----------- X X
gigas Cushman -------------------------- X --Mollusks.-The upper part of the Bohio formation in the Pacific coastal area yielded pectinids, but no other mollusks. On Barro Colorado Island the upper part of the formation yielded marine mollusks at two


27


localities (42d, 42i) and a mixture of marine, brackishwater, and fresh-water mollusks at a third locality (locality 42f). Howe recorded the presence of marine mollusks in carbonaceous sandstone penetrated in a core hole at the French lock site near Barro Colorado Island (Howe, 1908, p. 220-221).
The fossils from Barro Colorado Islands, all of which occur in subgraywacke interbedded with conglomerate, were received too late to be included in the systematic descriptions of chapter A of the present report. The species in the families covered by chapter A are as follows:

Mollusks from upper part of Bohio formation on Barro Colorado
Island (Trochidae to Turritellidae)
Localies
424 42f 42g
Solariella n. sp., cf. S. depress Dall --- ---- X
Neritina sp_ - -- - - X Hemisinus (Longiverena) n. sp., cf. I. atriformis
Cooke-..--------- -- _-- X
Crepidula? sp------------------------------- --X
Notica (Naticarius) sp--..-- - - ?
Polinices 9-------- -- ?
Sinum sp --------------------<
Gl bularia (Globularia) aff. G. flscleri (Dall) -? Pachycrommium aff. P. guppyi (Gabb) _------ X Turritella ef. T. altilira Conrad - ------- X
n. sp., aff. T. venezuelana Hodson ------- X -In chapter B of the present report, it is proposed to describe the new species in the preceding list and to redescribe the species identified as Globularia aff. G. fischeri. The last species mentioned is abundant at locality 42d and is the same as that from the Caimito and Culebra formations described under the same name on page 94. The fossils found on Barro Colorado Island are of late Oligocene age.
Age.-The basal part of the Bohio in the Quebrancha syncline contains smaller Foraminifera of early Oligocene age and the upper part of the formation in the Pacific coastal and Gatun Lake areas, respectively, contains late Oligocene larger Foraminifera and mollusks. Whether the formation represents so great a time span in each of the areas where it crops out is not known at present. It represents, however, more than the early Oligocene age previously suggested (Woodring and Thompson, 1949, p. 228). That it does not include all of the Oligocene is shown by the late Oligocene age of the overlying Caimito formation.
The larger Foralninifera in the upper part of the Bohio formation of the Pacific coastal area represent the widespread Caribbean Eulepidina fauna. That fauna and the Antiguan coral fauna that accompanies it at many localities is traditionally assigned to the middle Oligocene, because Vaughan correlated the Caribbean deposits with the Rupelian of northeastern Italy on the basis of the corals and because he thought a middle







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


Oligocene assignment fitted the occurrence of these fossils in southeastern United States (Vaughan, 1919a, p. 199-203, 207). The Eulepidina fauna is found in the Chickasawhay limestone of Alabama, the Suwannee limestone of Florida, aced the Flint River formation of Georgia usage, and the Antiguan coral fauna in the Flint River formation. These three formations are now assigned to the upper Oligocene (Cooke, Gardner, and Woodring, 1943, chart; MacNeil, 1944, fig. 1; Cole, 1952 (1953), p. 6). A middle Oligocene age is not unreasonable, if the American deposits that are essentially the equivalent of the European Aquitanian stage are assigned to the upper Oligocene. In the present report, however, they are referred to the lower Miocene. The age range of the Eulepidina-Antiguan coral fauna cannot be assumed to be narrowly restricted. It is a reef fauna and may eventually be found to have a considerable time range, like the Lower Cretaceous Urgovian reef fauna. In the Canal Zone and Panamd the Eulepidina fauna occurs in the upper part of the Bohio formation and at one locality in the Caimito formation (locality 51), and the closest approach to an Antiguan coral fauna is in the Caimito formation (localities 52 and 57). The time span between the deposition of the upper part of the Bohio in the Pacific coastal area and deposition of the Caimito at localities 51, 52, and 57 in the Gatun Lake area doubtless is not great, but it would be rash to correlate these deposits closely.
CAIMITO FORMATION EXCLUSIVE OF MADDEN BASIN AND PACIFIC COASTAL AREA
The Gatuncillo and Bohio formations are widespread, but are fairly uniform lithologically despite their widespread distribution. The Caimito formation is the youngest widely distributed formation. It is, however, lithologically heterogeneous. Deposits in too many areas have perhaps been included in the Caimito, but within the type region the formation is heterogeneous. In all the areas where the formation is identified it is marine, or at least mainly marine, and contains much volcanic debris.
The name for the Caimito formation was proposed by MacDonald (1913, p. 569). He did not properly define the name then or later, and lee specified no type region. In the absence of evidence to the contrary, it may be assumed that the type region was intended to be the region that furnished the name. Caimito, or Caimito Junction, was located on the present alinement of the Panama Railroad near Darien in the Gatun Lake area (MacDonald, 1913, pl. 68). On the basis of accepting the Darien region as the type region, the Caimito formation consists of the strata, mostly tuffaceous, overlying the Bohio formation. MacDonald included in the Caimito formation strata now assigned to the La Boca marine member of the Panama formation and his


representation of the Caicito as overlying the Enperador limestone (now assigned member rank in the Culebra formation) was based on misidentification of both Emperador and Caimito (MeacDonald, 1913, pl. 68).
In complete sections the Caimito formation overlies the Bohio formation or volcanic rocks that are thought to include the equivalent of the Bohio. Though the actual contact has not been observed, it evidentiv represents a discontinuity. In the northeastern part of the Gatun Lake area the Caimito seems to overlap the Bohio and Gatuncillo formations, directly overlying the basement complex, and in the northern part of Madden basin the Caimito overlaps the Bohio and rests on the Gatuncillo. In the southeastern part of the Gatun Lake area the lower part of the Caimito (or perhaps the entire formation), appears to grade into the Las Cascadas agglomerate. Wherever the Caimito formation is dated it is of late Oligocene age, except in Madden basin, where it includes both upper Oligocene and lower Miocene deposits. The Caimito of that area is described under the heading "Oligocene and Miocene series.' The Caimito of the Pacific coastal area, which is entirely of Oligocene age, appears to be continuous with the Oligocene part in Madden basin and is discussed under the same heading.
According to estimates, the thickness of the Caimito ranges from 250 to 400 meters.
STRATIGRAPHY AND LITHOLOGY
Gatun Lake area.-Three members of the Caicmito formation were recognized by Jones in the Gatun Lake area: lower, middle and upper (Jones, 1950, p. 900-901), which correspond, respectively, to the basal, lower, and upper members of his former usage (Woodring and Thompson, 1949, p. 232-233). According to Jones, the lower member is made up of conglomerate and tuffaceous sandstone. The conglomerate resembles conglomerate of the underlying Bohio formation, but includes pebbles of tuff. The sandstone and the matrix of the conglomerate contain acidic tuff. The lower member is correlated by Jones with the Las Cascadas agglomerate, but perhaps the entire formation is to be correlated with the Las Cascadas. The lower member of the Caimito is recognized only locally. Its absence elsewhere may indicate discontinuity or lateral gradation into deposits grouped with the middle member.
The middle member consists chiefly of tuffaceous sandstone, some of which is calcareous, and lenticular limestone, mostly algal limestone. Tuff, tuffaceous calcareous siltstone, and conglomerate are other constitutents. Agglomerate and poorly sorted, coarsegrained, tuffaceous, nonmcarine sandstone in the northeastern part of Barro Colorado Island evidently are the equivalent of marine strata in the middle member. Foraminiferal soft limestone, such as that at locality


28









54f, doubtless corresponds to the foraminiferal marl of publications issued before the flooding of Gatun Lake. Foraminiferal marl was exposed at localities on Rio Clagres, including Penia Blanca, the type of locality of Lepidocyclia canellei. The approximate location of Penia Blanca is shown as locality 55 on plate 1. Hill claimed that foraminiferal marl could be seen to rest unconformably on conglomerate (of the Bobio ,formation) near Bohio (Hill, 1898, p. 178-179), but Howe (1907, p. 113) was unable to recognize the locality Hill described. The rhyolitic tuff on Rio Chagres at Barbacoas, where the original line of the Panama Railroad crossed the river about 9 kilometers west of Gansboa, presumably is to be included in the Caimito. The tuff was found to be so similar to tuff in the Panami formation that Hill (1898, p. 201), Bertrand and Ztlrcher (1899, p. 91), and Howe (1907, p. 117) did not hesitate to correlate them. Though no data are available on the comparative volcanic constituents of the different formations, the correlation 'is not accepted (p. 41). Hill casually used the expression "Barbacoes formation" for the tuff and "San Pablo phase of the Barbacoas formation" or "San Pablo formation" for underlying rock lie described as ,conglomerate of volcanic material (Hill, 1898, p. 184-185, 187).
Tuff, agglomeratic tuff, tuffaceous siltstose, and discontinuous sandy tuffaceous limestone are the principal constituents of the upper member, the thickest and most widespread part of the formation (Jones, 1950, p. 901).
The thickness of the Caimito in the Gatun Lake area is estimated to be at least 100 meters and may be considerably more.
Rio Mandinga area.-Along a tributary of Rio Mandinga, west of the canal and south of Gamboa, the Caimito formation is characterized by a unit of conglomerate and conglomeratic sandstone that has a thickness of between 75 and 100 meters. Conglomerate is not rare in the Caimito of other areas, but it consists of thin scattered beds. The unusual thickness of conglomerate prompted Jones to propose the name "Caraba facies of the Caimito formation" (Jones, 1950, p. 901). The conglomerate is overlain by fossiliferous silty calcareous sandstone (localities 59 and 60) and limestone. Locality 61 represents coralliferous limestone in this area.
The distribution of the conglomerate is unknown. The extensive area farther west along the south border of Gatun Lake, shown on plate 1 as doubtfully underlain by the Caimito formation, has not been examined.
Quebranche syncline.-The Caimito formation of the Quebrancha syncline consists of two members: in ascending order, the Quebrancha limestone member
413788-57---3


and the calcareous siltstone member. They save been mapped and described by Thompson (1944, p. 17-21). The economically important Quebrancha limestone member, which is quarried for the manufacture of cement, was named by Thompson (1944, p. 17) as a separate formation. The type region is on the east limb of the syncline and includes the quarry of the Panama Cement Company. The Quebrancha member has a thickness of 110 to 135 meters. Subsurface explorations and outcrops reveal that it is made up, in ascending order, of three parts: calcareous siltstone and calcareous medium-grained sandstone, limestone and thin partings of calcareous siltstone, and somewhat marly foraminiferal limestone consisting for the most part of closely packed specimens of Lepidocyclina. The foraminiferal limestone is by far the thickest part.
The calcareous siltstone member, which gradationally overlies the Quebrancha limestone member, includes calcareous siltstone, tuffaceous pumice-bearing siltstone, and calcareous medium-grained sandstone. This member has an estimated thickness of 150 meters and is the youngest unit in the Quebrancha syncline.
Rio Chagres area.-The lowland along Rio Chagres north-northeast of Gamboa probably is underlain by the Caimito formation, but only a small part of it southwest of Nuevo San Juan was examined. Calcareous coarse-grained pebbly sandstone at locality 93 and limestone and siltstone farther west contain Foraminifera, including orbitoids identified in the field as Lepidocyclina canellei and L. saughani. Limestone exposed at and near Las Cruces before the flooding of Gatun Lake yielded a few mollusks (localities 94, 94e).

FOSSILS AND AGE
Larger Ioraainifera.-Larger Foraminifera are widespread and locally abundant in the Caimito formation of the areas just described, particularly in limestone and calcareous siltstone. No fossils of any kind, however, are known in the lower member in the Gatun Lake area and larger Foraminifera from one locality are the only fossils available for the upper member in that area. Douvill6 recorded larger Foraminifera and calcareous algae in collections from localities near Pefia Blanca and Bohio Soldado, and expressed the opinion that they are Oligocene (Douvilli, 1891, p. 498, 499). Later he identified the small orbitoid from Peia Blanca as Lepidocyclina and reaffirmed the Oligocene age (Douvil6, 1898, p. 598-599). This small species, one of the most common in the Caimito, was still later named L. canellei for the collector, an engineer of the first French company (Lemoine and R. Douvill6, 1904, p. 20). L. vasghani, another common species, is extraordinarily abundant in the Quebrancha limestone


29


GEOLOGY







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


member. The type locality of L. vaughani is in the type region of the Caimito formation on the Panama Railroad near Darien: locality 49, which was referred to the Emperador limestone member of the Culebra formation by MacDonald and Vaughan (MacDonald, 1919, p. 539, locality 6021). Seven samples of larger


Foraminifera were submitted to W. S. Cole, who identified the species in the following table. Recently Cole (1957, p. 314) also recorded 8 species from their Caimito of Barro Colorado Island, all except one ob which occur in the Caimito elsewhere. The exception is Archaias compressus, which is still living.


Larger Foraminifera from Caimito formation of Gatun Lake area, Rio Mandinga area, and Quebrancha syncline
[Cole, 1952 (1953), p. 7]
Localities

Gatun Lake area Ma- b dinga cha area syn.
Cline


Operculinoides panamensis (Cushman)-__ ---____-..__-__-_-___ --_____ ------Heterostegina antillea Cushman ----_ -- ______._____ ____- -----------------------israelskyi Gravell and Hanna--------------------------------------------------panamensis Gravell--------------------------------------------------------------Lepidocyclina (lepidocyclina) asterodisca Nuttall-----------------------------------------(Lepidocyclina) canellei Lem oine and R D ouvillM _----_- _- __-__-parvula C ushm an _-- __- .---_ -- _________- _____---------------------------waylandvaughani Cole ------ ---- ---------------------------------yurnagunensis Cushman------------------------------------------------------yurnagunensis morganopsis Vaughan-_-_-____ ---_ -___- _-----(Nephrolepidina) dartoni Vaughan_ _- ____- __-- _______-_-_---------------------tournoueri Lemoine and R. Douvill6
vaughani Cushman-- ----_- ___- ____--------------------------------(Eulepidina) undosa Cushman------------------------------------------------------Miogypsina (Miogypsina) antillea (Cushman)--------------------------------------------(Miolepidocyclina) panamensis (Cushman)-------------------------------------------


Middle member


48 51


53


I __________________ I -


X


X

/
X


X

X


x



x


X

X


56a

X

X
X


X

X


X


Upper mem
ber


No members recognized


58 59


X


X


X


Quebran-. cha lime. stone mem
ber
62a


X

x


x
x
X

X

X
X


_I __ I I I I I I


All the species in the preceding table occur elsewhere in deposits of late Oligocene age. Though the table does not include the calcareous siltstone member of the Quebrancha syncline, Lepidocyclina canellei has been recognized by R. H. Stewart in that member (Woodring and Thompson, 1949, p. 234).
Corals.-MacDonald and Vaughan found corals in the middle member of the Caimito formation of the Gatun Lake area at localities 52 (Geological Survey 6024b) and 57 (Geological Survey 6026). Locality 52 was assigned to the Emperador limestone [member of the Culebra formation] and locality 57 to the Culebra


formation (MacDonald, 1919, p. 540, 541). Four of the seven species identified by Vaughan occur in the upper Oligocene Antigua formation of the island of Antigua and one in the lower Miocene Anguilla formation of the island of Anguilla (Vaughan, 1919a, p. 208, 209). Numerous specimens of a coral in limestone of the Caimito at locality 61 in the Rio Mandinga area is identified by J. W. Wells as Goniopora cf. G. cascadensis.
Mollusks.-Mollusks have been found in the areas described in the preceding pages, but they are nowhere abundant. The species covered in chapter A of the present report are as follows:


30


T


4








Mollusks from Caimito formation of Gatun Lake area, Rio in the Gatun Lake area, the age of which is unknown,
Mandinga area, and Quebrancha syncline (Calyptraeidae to
Turritellidae) i tentatveoy groped .ith tht middle and tpper nootboro ao iato Oligocono.


Locaite
Rio Que.
X50 e branGatan Lake area dinga banNo branMiddle member 0 loe
recogmSton
otood meN7er
56 57 57a 60 62


Trochita cf. T. trochiformis (Born) -- Netica (Naticarius?) spSinum sp - -_Globularia (Globularia) aff. G. fiocheri
(D a ll) .... - _ _- .- _- ._ ._
Pachycrommium? cf. P.? trinitatensis
(M ansfield) -- _------- __ ------Turritella meroensis Olsson _-_- _(Torcula) altilira Conrad, subsp--


? X X X


Collections of mollusks from Barro Colorado Island and Pato Horqueto Island are not included in the systematic descriptions of chapter A of the present report. (Pato Horqueto Island is one of the Brujas Islands northwest of Barro Colorado Island.) The Barro Colorado collections, which represent a moderate-depth facies, contain unidentified species of Solariella? (locality 541), Calyptraea? (locality 54m), Natica (Natica?) (locality 54k), Polinices (locality 54h and probably localities 54j and 54k), and Neverita? (locality 54m). Conglomerate on Pato Horqueto Island yielded mollusks of shallow-water facies, including Calyptraea sp., Sinum sp., Ampullinopsis spenceri, and Turritella sp. Ampullinopsis spenceri, a representative of a genus mainly of Oligocene age not found heretofore in the Canal Zone, is to be described in chapter B.
Echinoids.-Fragmentary remains of Clypeaster are fairly common in some areas. C. W. Cooke identified a complete specimen from locality 60 as C. concars.
Age.-A late Oligocene age for the fossiliferous parts of the Caimito in the areas described in the preceding pages is indicated by larger Foraminifera, corals, and mollusks. Most of the mollusks just listed would not be out of place in either upper Oligocene or lower Miocene deposits. Ampullinopsis spenceri [late Oligocene of Antiguo, Puerto Rico(?), western Panoima(?), Ecuador(?), and Perd(?)] and Turritella meroensis (late Oligocene of western Panam6, Ecuador, and Perd) however, indicate late Oligocene. The lower member


TUFFACEOUS STRATA IN CHORRERA AREA
Tuffaceous strata in the Chorrera area, west of the Canal Zone and south of Gatun Lake, are shown by a separate pattern on the geologic map (pl. 1) in a region of undifferentiated volcanic rocks. Though the unnamed tuffaceous strata consist principally of tuffaceous siltstone, tuffaceous sandstone, and tuffl, they include bentonitie clay, conglomerate, and agglomerate. Leaf bnprints are the only fossils that have been found. The unnamed strata, w which may be the equivalent of part of the Caimito formation of the Gatun Lake area, are doubtfully referred to the late Oligocene.

BAS OBISPO FORMATION AND LAS CASCADAS AGGLOMERATE
The Oligocene formations so far described contain more or less volcanic material, mostly in the form of tuffareous debris. The Bas Obispo formation and Las Cascadas agglomerate are entirely volcanic. They are interpreted to represent pyroclastic rocks and minor flows that accumulated at the periphery of a volcanic pile. The center of the pile evidently was west of the Canal Zone south of the continental divide, but presumably is concealed by later flows. At all events that region is characterized by thick volcanic rocks. Still farther out from the center of the volcanic pile the Bas Obispo formation and Las Cascadas agglomerate are thought to grade, respectively, into the Bobio and Caimito formations.
The volcanic rocks now included in the Bas Obispo formation and Las Cascadas agglomerate were described as massive igneous rocks by Hill (1898, p. 189-191), and as "roche de Gamboa' by Bertrand and Zrcher (1899, p. 89). They were named the Obispo formation or Obispo breccia by Howe (1907, p. 110-111). The emendation to Bas Obispo formation and the splitting off of the younger part as the Las Cascadas agglomerate were proposed by MacDonald (1913, p. 568). The type region of both formations is in the northern part of Gaillard Cut, where they are the oldest exposed formations. Their thickness is unknown, but the combined thickness is presumably several hundred meters. According to plate 1, near Gamboa the Las Cascadas agglomerate rests on the Bohio formation, the Gatuncillo formation, or the basement complex. Confirmation of this overlap is needed.

STRATIGRAPHY AND LITHOLOGY
The Bas Obispo formation and Las Cascadas agglomerate probably would ordinarily be combined as one formation. They differ, however, in induration and


GEOLOGY


31







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


therefore have different properties in excavations. Both crop out in the northern part of Gaillard Cut. and in'the Gamboa area northwest of the cut. The Las Cascadas agglomerate extends farther west along the canal than the Bas Obispo formation. To the southwest both merge into undifferentiated and unmapped volcanic rocks.
According to Howe and MacDonald (in the publications just cited) and to accounts published by geologists of the Geological Section of the Special Engineering Division, both formations consist principally of agglomerate and tuff. The matrix of agglomerate of the Bas Obispo is hard sandy tuff so firmly indurated that the rock breaks through the larger constituents. Crude bedding is apparent in local thin deposits of the Bas Obispo made up of imperfectly rounded pebbles and cobbles. Such rock is not as well indurated as the agglomerate. The matrix of agglomerate of the Las Cascadas consists of soft fine-grained altered tuff and bentonitic clay. Beds of tuff in the Las Cascadas also are softer than those of the Bas Obispo. Both formations include andesitic and dacitic flow breccias and both are cut by a few andesitic dikes and by numerous basaltic dikes.
AGE
Fossils have not been found in either the Bas Obispo or Las Cascadas. They are doubtfully referred to the Oligocene because of their inferred relations to the Bohio and Caimito formations (p. 25, 28). The Bas Obispo and Las Cascadas presumably represent most of the Oligocene, not only early Oligocene as previously suggested (Woodring and Tiiompson, 1949, p. 228).

OLIGOCENE AND MIOCENE SERIES
CAIMITO FORMATION OF MADDEN BASIN AND PACIFIC COASTAL AREA

The Caimito formation of Madden basin, unlike that of other areas, includes both upper Oligocene and lower Miocene deposits. As shown on plate 1, in the northern part of the basin the Bohio formation is overlapped by the Caimito. The thickness of the Caimito in the basin appears to be about 450 meters. The deposits now referred to the Caimito formation were designated the Culebra formation, Emperador limestone, Caimito(?) formation, and Gatun(?) formation by Reeves and Ross (1930, p. 14-17).
The strata in the Pacific coastal area assigned to the lower part of the Caimito appear to be a direct extension of that part in Madden basin. These strata in the Pacific coastal area have an estimated thickness of not more than 250 meters.


STRATIGRAPHY AND LITHOLOGY
Madden basin.-Five members are tentatively recognized in the Caimito formation of Madden basin. The only formal member names that are used areI those that have already been proposed, for detailed work may show that some arrangement other than that adopted in the present report is preferable. Two members are grouped as the lower part of the formation and the upper three as the upper part. In the follow-ing paragraphs the members are described in upward stratigraphic sequence.
The calcareous sand stone-siltstone member overlies the Bohio formation or overlaps it and rests on the Gatuncillo formation. Sandstone of this member, ranging from very fine-grained to very coarse-grained and conglomeratic, is well exposed on Rio Chilibrillo upstream and downstream from the bridge on the road from Buenos Aires to Casa Larga. The sandstone is variably tuffaceous, and at least on Rio Chilibrillo the member includes massive coarse-grained tuff. The exposures on Rio Chilibrillo indicate a thickness of" at least 200 meters.
The pyroclastic-clay member includes agglomerate, tuff, bentonitic clay, conglomerate, and limestone. Agglomerate may be seen on the Transisthmian Highway near Rio Chilibre on the east side of the basin. The strata on the east side of the basin also include three lenses of limestone, two of which are exposed on the Transisthmian Highway. The thickness of the member on the east side of the basin is about 110 meters. On the west side of the basin, where the member is represented by steeply dipping clay immediately north of Rio Chagres and just west of the Transisthmian Highway, the thickness is probably not more than 50 meters.
The Chilibrillo limestone member-the lowest member in the upper part of the formation -consists of lenticular limestone that has a maximum thickness of about 30 meters. Detailed mapping may show that limestone of that thickness lies at more than one horizon. The name Chilibrillo was casually used by Olsson (1942, p. 234). The type region is on the east side of the basin near Rio Chilibrillo. Entrances to caves in the limestone are located at locality 81, about 150 meters west of the Transisthmian Highway, and nearby.
The calcareous sandstone member overlies the Chilibrillo limestone member, or in its absence overlies the pyroclastic-clay member and in that event is at the base of the upper part of the formation. The most accessible exposures of the medium-grained


32






GEOLOGY


calcareous and tuffaceous sandstone are on the east side of the basin along the Transisthmian Highway. Highly calcareous sandstone is exposed at the north abutment of the Transisthmian Highway bridge across Rio Chagres. The thickness of this member is about 30 meters.
The Alhajuela sandstone member is confined to a small area in the central part of the basin at and near Madden Dam. Before the construction of the dam the village of Alhajuela was located on Rio Chagres opposite locality 85. (For location of Alhajuala see Reeves and Ross, 1930, pl. 5.) The massive fine- to coarsegrained tuffaceous sandstone forms the foundation of Madden Dam and the gorge of Rio Chagres below the dam. Plate 7 is a view at the dam site. Fossil shells are more conspicuous in this member than in any other part of the Caimito formation in Madden basin. The thickness of the Alhajuela is 85 meters. The name, in the form "Alajuela sandstones", was proposed by Olsson (1942, p. 234, 243). The restricted usage suggested by his chart (Olsson, 1942, p. 234) is adopted in the present report.
Pacific coastal area.-The lower part of the Caimito formation appears to extend continuously from Madden basin to the Pacific coastal area. Agglomerate, tuffaceous sandstone, tuffaceous conglomeratic sandstone, and conglomerate in the region between the basin and the coastal area are thought to represent the lower part of the Caimito. The geology of this intermediate region, however, is complicated by numerous intrusive stocks, and the succession of sedimentary strata and their relations to those in adjoining areas have not been worked out. Limestone at locality 97, just east of Madden Highway, contains a small Lepidocyclina suggesting L. canellei on the basis of field identification.
In the Pacific coastal area the lower part of the Caimito is made up mainly of tuffaceous siltstone, tuffaceous sandstone, and conglomerate. Algal limestone, like that at localities 95 and 96, is a minor constituent.
FOSSILS AND AGE
Smaller Foraminfera.-Smaller Foraminifera were found in the calcareous sandstone-siltstone member of Madden basin on Rio Chilibrillo: in silty very finegrained sandstone at locality 68 and in sandy siltstone at locality 70. These collections have not been identified.
Larger Foraminifera.--Lepidocyclina vaughani is widespread and abundant in the calcareous sandstone-siltstone member on the west side of Madden basin, ranges throughout that member in the exposures on Rio Chilibrillo, and occurs in the lower part of the formation in the Pacific coastal area. Despite an apparently favorable depositional environment, no orbitoids were


33


observed in limestone of the pyroclastic-clay member in Madden basin. In fact, an Archaias-like species is the only larger foraminifer noticed in limestone of that member. The species in the table that follows were identified by Cole.

Larger Foraminifera from lower part of Cainito formiation of
Madden basin and Pacific coastal area atole, 1952 (193), p. 7]
Locaities


Ileterostegina antillea Cushman _-_ Lepidocyclina (Lepidocyclina) canellei Lemoine and R. Doutttd -parvula Cushman _--- ___o
yurnagunensis morganopsis Vaughan
(Nephrolepidina) vasghani Cushman-Miogypsina (Aliogypsina) antillea Cushm a n _ -- - - - -- - - --_ - - _


maddenn cifc
basin coast64 67 69 95


--- ------_ _X
X X X X
- - - - X


Mollusks.-Mollosks occur in the Caimito of Madden basin, but none was found in the Pacific coastal area. Limestone in the pyroclastic-clay member (localities 71-73) and submerged calcareoos strata of the lower part of the Caimito (localities 65, 66) contain mollusks, but none of tle families covered by chapter A of the present report is represented in the collections. The typical form of Turritella altilira occurs in the Alhajuela sandstone member at locality 89. Specimens of '. altilira from the Alhajuela at localities 88 and 92, and from the underlying calcareous sandstone member at localities 77 (T. cf. T. altilira) and 80, are not sufficiently well preserved to determine whether they represent the typical form. Turritella gatunensis was found in the calcareous sandstone member (locality 82).
Echinoids.-According to identifications by C. W. Cooke, Clypeaster lanceolatus occurs in limestone of the pyroclastic-clay member (locality 71) and in submer-ed calcareous strata of the lower part of the Caimito (locality 66), and Clypeaster cf. C. pinarensis in the calcareous sandstone member (locality 84a).
Age.-The lower part of the Caimito formation in Madden basin, consisting of the calcareous sandstonesiltstone member and the pyroclastic-clay member, and the formation in the Pacific coastal area are considered of late Oligocene age, like the entire Caimito of other areas. The two species of larger Foraminifera from the calcareous sandstone-siltstone member in Madden







34 GEOLOGY AND PALEONT

basin and the five species from the Pacific coastal area are typical Caimito species and typical upper Oligocene species. The age of the pyroclastic-clay member of Madden basin is based principally on an early species of Nodipecten found also in the middle member of the Caimito in the Gatun Lake area.
The upper part of the Caimito in Madden basin, consisting of the Chilibrillo limestone member, the calcareous sandstone member, and the Alhajuela sandstone member, is assigned to the early Miocene on the basis of mollusks. The lower two members would be referred to the late Oligocene by those who claim that the Aquitanian and its essential American equivalents are of late Oligocene age. The Alhajuela sandstone member, however, is late early Miocene; that is, younger than the disputed Oligocene or Miocene. That it may include early middle Miocene, as suggested in a preliminary account (Woodring and Thompson, 1949, p. 236), appears to be unlikely.
Only the Oligocene part of the Caimito is recognized in the Pacific coastal area. It is overlain and perhaps partly overlapped by the Panamd formation, which is correlated with the lower part of the Miocene strata in the Caimito of Madden basin. No fossiliferous strata as young as the Alhajuela sandstone member have so far been found in the Pacific coastal or Gaillard Cut areas.
MIOCENE SERIES
CULEBRA FORMATION, INCLUDING EMPERADOR LIMESTONE MEMBER
The Culebra formation is recognized along and near the canal in the Gaillard Cut area and immediately to the southeast in the region straddling Pedro Miguel Locks. (For a large-scale map of the Gaillard Cut area see plate 2.) To the southwest presumably it merges into undifferentiated and unmapped volcanic rocks, like other formations in the Gaillard Cut area. The Culebra itself contains volcanic debris, but not nearly so much as the underlying and the overlying formations. The name for the formation, in the form "Culebra clays," was first used by Hill (1898, p. 192195). The type region is in the central Gaillard Cut area, where the town of Culebra was located on the west side of the canal before and during the construetion period. The Culebra formation unconformably overlies the Las Cascadas agglomerate. The maximum thickness of the formation is about 150 meters. The thickness decreases northward, evidently as a result of overlap of successively younger parts of the formation on the Las Cascadas agglomerate.
Coralliferous limestone exposed in a quarry near Empire attracted attention at an early date and was named the Empire limestone by Hill (1898, p. 195-196). MacDonald (1913, p. 569) changed the name to Em-


'C


LOGY OF CANAL ZONE

perador limestone, presumably because of the possibility of confusion with the Empire formation of Oregon. Empire was the American name for a tow; near Culebra, whereas the French used the Spanish, name Emperador for the same town. The town was located on the pre-construction alinement of the Panama Railroad near Culebra, approximately ati' locality 117 as plotted on plate 2. The quarry near Empire (locality 118 of plate 2), which is to be regarded,. as the type locality of the Emperador limestone member, is overgrown and unrecognizable, and so is the similar limestone formerly exposed on a street in Empire. Limestone agreeing with descriptions of the Emperador is still exposed along the canal. These beds of relatively pure coralliferous limestone probably are at different horizons in the upper part of the CulebraJ formation and probably grade southeastward into calcareous sandstone (Woodring and Thompson, 1949, p. 237). Should it be demonstrated that the name is being used for limestone at different horizons, the name should be abandoned, except for the limestone at the' type locality. In that event, however, a formal name would hardly be needed for a single locality, even if the locality were again found. In the meantime no serious errors should result from usage of the name. The coralliferous limestone has a maximum thickness of 15 meters. It therefore is a minor constituent and is given member rank in the Culebra formation.
The Emperador limestone member of the Culebra formation is known to occur only in the northern part of the outcrop area of the Culebra. MacDonald's representation of the Emperador as widespread and resting unconformably on formations of different age was based on misidentification of limestone in several. formations (MacDonald, 1913, pl. 68). According to present interpretations, coralliferous limestone in the La Boca marine member of the Panama formation on Rio Masambi, in the Gaillard Cut area, was recently misidentified as Emperador (Woodring and Thompson, 1949, p 237).
STRATIGRAPHY AND LITHOLOGY
Stratigraphic secLions of the Culebra formation in Gaillard Cut have been published by MacDonald (1919, p. 535-539) and he also published structure sections of part of the cut (Natl. Acad. Sci., 1924 figs. 4, 5, op. p. 52). He divided the Culebra into lower and upper parts. The lower part consists chiefly of dark-colored, thin-bedded or laminated, fine-grained rocks: carbonaceous or lignitic shale, carbonaceous silty mudstone, tuffaceous siltstone. It includes, however, minor beds of tuffaceous and calcareous sandstone and conglomerate. The upper part is characterized by calcareous and sandy strata ranging in thickness from 0.3 to 3.5







GEOLOGY


aneters and in composition from tuffaceons and pebbly alcareous sandstone to sandy limestone. The calareous and sandy strata are separated by dark calcareous or somewhat carbonaceous shale and mudstone. Carbonaceous strata in both parts of the formation contain land plant debris, including identifiable leaves (Berry, 1918).
Generally the Culebra formation is overlain directly by conglomerate at the base of the Cucaracha formation, marking a discontinuity, evidently a minor discontinuity. On both sides of Gaillard Cut, however, just northeast of the site of Culebra, somewhat calcareous silty sandstone and sandy siltstone interbedded with clay like that of the Cucaracha form a transition .zone between the two formations. The transition zone is included in the Culebra formation. Sluicing operations carried on in 1947 on the west side of the canal, in the region where the transition zone is represented, exposed the section below. Unit 1 is at the level of the canal.



Section of upper part of Culebra formation, including transition
zone between Culebra and Cucaracha formations, on west side
of Gaillard Cut at canal station 1759 2 near site of Culebra

Trnsition zone between Culebra and Cucaracha formations: MeS,
15. Clay, dark-gray, slickensided, and silty carbonaceous clay. Overlain by light-gray mediuigrained locally conglomeratic sandstone taken
as base of Cucaracha formation __-----__- 4. 6
14. Siltstone, limonitic-weathering, dark-gray; few
gypsiferous shell tips of Turritella weathered
out __--_--___-----___- __-_----------- .
13. Siltstone, dark-gray, sandy; includes a 15-cie
fossiliferous somewhat calcareous layer at base (locality 112) and fossiliferous calcareous concretions at and within 30 cmi of top
(locality 112a) -_--_ __----_--------- 1. 0
12. Clay, greenish-brown, slickensided, silty ---___ 5
11. Sandstone, greenish-gray, silty, medium-grained;
and siltstone ------------_--------- - 1. 6
10. Sandstone, broNitish-gray, silty, mediumgrained; and siltstone containing petrified
wood _-_-_-_--------------- 1. 1
9. Clay, limnioniitic-weathering, slickensided, darkgray ----_-_--------- 1.3
8. Clay, grayish-green, somewhat carbonaceous
and somewhat fissile ------ 2. 3 Culebra formation proper, upper part:
7. Sandstone, light-gray, medium-grained, poorly
sorted, silty, calcareous; siltstone partings-_- 1. 5
6. Shale, dark-gray, silty, somewhat carbonaceous;
includes thin layers of calcareous sandy siltstone -----_---------_ --.------- 1. 3
3 The canal stations are located at intervals of 100 feet (30 meters) along the center alinement and are numbered from the Caribbean terminus to the Pacific terminus. Strictly speaking the rock exposures are opposite the stations, not at them.


35


Section of upper part of Culbra formation, including transition
zone between Culebra and Cucaracha formations, on west side of Gaillard Cut at canal station 1759 near site of CulebraContinued Meer


5. Sandstone, light-gray, medium- to coarsegrained, poorly sorted, calcareous; siltstone
partings
4. Shale, dark to black, calcareous, somewhat
carbonaceous
3. Sandstone, light-gray, medium- to coarsegraited, poorly sorted, calcareous, it beds 30 to 90 cim thick and interbedded with poorly exposed somewhat carbonaceous shale.
Includes a 15-ct layer of conglomerate - 2. Sandstone, coarse-grained to conglomeratic,
calcareous; contains a ioderately large smooth species of oyster -- _-- -_----1. Sandstone, light-gray fine- to tmediu-i-grained,
poorly sorted, calcareous, in beds 30 cm thick and interbedded with dark to black calcareous and carbonaceous shale and sudstone. Locality 108, 1.5 tn above edge of c a n a l _-- - - .- .- - _- _- - _- .. .


3. 2 1. 4 51









4. 2


Thickness of section--------- -----33. 5

Part of the transition zone is exposed on the east side of the canal at canal stations 1754. Fossiliferous strata corresponding to the fossiliferous parts of bed 13 of the preceding section are recognizable on the east side, but the best-preserved fossils are weathered out and were put in one collection (locality 110). Silicified wood is common at that locality, including segments of logs riddled with shipworm tubes (Teredo).
Limestone of Emperador type in the upper part of the Culebra crops out farther northwest on the west side of the canal on both limbs of a syncline near the site of Las Cascadas. At locality 120 (canal station 1600) the limestone is 6 meters thick and in a nearby core hole is 24.3 meters above the base of the Culebra. At locality 121 (canal station 1619, pl. 8) the thickness is 15.2 meters and the limestone is about 27.5 meters above the base of the Culebra. At both localities the underlying strata consist of dark carbonaceous clay and tuffaceous siltstone. The basal 30 to 60 centimeters of the limestone at locality 120 is silty and contains numerous pectinids. The limestone at locality 121 includes a basal calcareous siltstone bed that has a thickness of 15 to 30 centimeters and a middle calcareous siltstone bed 2.4 meters thick. The limestone at these two localities appears to represent the same zone and probably is the same as limestone near Tower N, a signal tower on the pre-construction line of the Panama Railroad near Las Cascadas. Fossils from "the Pecten bed" near Tower N were recorded by Brown and Pilsbry (1913, p. 502-503). The limestone in the Las Cascadas area is presumed to be the equivalent of







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


calcareous sandstone in the measured section at canal station 1759. MacDonald (1919, p. 537) assigned to the Emperador "somewhat sandy limestone" at locality 99g (canal station 1606). The matrix of the numerous fossils MacDonald collected at that locality consists of sandy limestone that does not resemble the Emperador limestone.
FOSSILS AND AGE
Smaller Foraminifera.-A few species of smaller Foraminifera from the Culebra formation were recorded by Cushman (1918). Some of the localities referred to the Culebra in Cushman's publication represent other formations: Geological Survey localities 6009 and 6010 represent the La Boca marine member of the Panama formation; localities 6024a, 6025, and 6026 the Caimito formation. Though the fauna of the Culebra is not extensive, more species than the few recorded by Cushman are represented in core collections obtained during the operations of the Geological Section of the Special Engineering Division. Meager collections can still be obtained at outcrop localities, such as localities 104 and 108. It has been claimed that Siphogenerina transversa is not found in the Culebra formation (Woodring and Thompson, 1949, p. 241). M. N. Bramlette, however, identified a small specimen of that species in core material from a depth of 88 feet (26.7 meters) in core hole SL108 and another small specimen from a depth of 133 feet (40.4 meters) in the same core hole. Core hole SL108 was located 1.1 kilometers westsouthwest of locality 101 and evidently the Culebra formation was penetrated at the depths just specified.
Larger Foraminifera.-Cushman's identifications of the species of Lepidocyclina in the Culebra formation have not been confirmed (Cushman, 1918a,p.90). H.G. Schenck identified Lepidocyclina canellei in core samples at horizons 30 to 45 meters below the top of the Culebra (Woodring and Thompson, 1949, p. 238). Cole recently described and illustrated L. miraflorensis (locality 99g) and L. waylandvaughani (locality 99a) from the Culebra formation proper, and L. miraflorensis (locality 119a) from the Emperador limestone member (Cole, 1953a). The type localities of Miogypsina cushmani (locality 107) and "Orbitolites" americana


(locality 100) are in zthelCulebra formation. Mioj gypsina intermedia is recorded from the Culebra at locality 115 near Paraiso (Drooger, 1952, p. 36).
Corals.-Of the four species of corals recorded by Vaughan from the Culebra formation proper, one occurs' in the Emperador limestone member, three in the Antigua formation, and all in the Anguilla formation (Vaughan, 1919a, p. 208; Geological Survey locality 6026 represents the Caimito formation). Vaughair listed 24 species of corals from the Emperador limestone member. Four of them occur in the Antigua formation and nine in the Anguilla formation (Vaughan, 1919a, p. 209; Geological Survey locality 6024b represents the Caimito formation and 6256 the La Boca marine member of the Panami formation).
Molluskls.-MacDonald made numerous collections of mollusks from the Culebra formation during the excavation of Gaillard Cut. Much of the material, however, is poorly preserved. Except in the Paraiso area, the Culebra fauna includes species indicating brackish water, particularly in the transition zone between the Culebra and Cucaracha formations (localities 110 to 112a). The Neritina, for example, indicates brackish water and Littorina angulifera is a modern species that lives in mangrove swamps. Most of thespecies indicating brackish water are absent in the Paraiso area (localities 113 to 116). Plate 2 indicates that the fossiliferous strata in the Paraiso area are, close to the top of the Culebra. It has been suggested that the uppermost part of the formation in the Paraiso area is the equivalent of the transition zone but represents an environment farther seaward (Woodring and Thompson, 1949, p. 239). According to the evolutionary scheme worked out by Drooger for miogypsinids, however, Miogypsina intermedia, which occurs in the Paraiso area, is less advanced than M. cushmani, found in the upper part of the Culebra farther northwest (locality 107), where the transition zone is not known to be present (Drooger, 1952, fig. 17, p. 72).
The following mollusks are in the families covered by chapter A of the present report:


36








GEOLOGY

Mollusks from Culebra formation, exclusive of Emperador limestone member (Neritidae to Turritellidae)


98 99a 99b 99c 99d 9f 99g 99h 100 100b 104b 106


Aeritina (Vitla?) sp Littorina aff. L. angulifera
(Lamarck) ---Rissoina (Zebinella?) sp Xenophora sp Hipponix? sp
Crepidula sp Calyptraea cf. C. centralis
(Conrad) Trochita'? cf. T. trorthiformtis
(Born) -Crucibulum sp Natica (Naticarius?) sp -Polinics? sp
Neverita? sp -- Sinum sp - Globularia (Globutaria) off. G.
fischeri (Dall) -Pachycrommium? cf. P.? trnitatensis (Mansfield) -cf. P. guppyi (Gabb)
Turritella (Torcula?) amaras
Woodring, n. sp _.-
sp --cf. T. subgrundifera Dall venezuelana Hodson.--- ---.
rf. T. berjadinensis cocoditana Hodson ----------


107 1t0 108cl 110


110a 111a 111 112 112a 114 115a 115b 116


-- -- - -- -

-xx- -- --- -- --- ---
- -- -- -- -- - --- -- - -- -- ---

X- _--- --- -- -.-- --+ -- ---


--- --- --- -- - -- -- X X X
--- --- - - -- -- X - -- --
---
------- --- --- X X -X -.- X X -
- -- X X ---


- - - - - ---

X ------. X -- -X X X X X --- -- --- X


X --X X X -- -- -- .-- X -


Collections from the type locality of the Emperador member contain only a few species of mollusks, none of which represents the families described in chapter A of the present report. Limestone in the Las Cascadas area assigned to the Emperador contains Neverita? sp. (localities 119a, 120) and Turritella altilira in the unrestricted sense (locality 120).
Echinoids.-Clypeaster lanceolatus and Echinolatpas semiorbis were recorded from the Emperador limestone member by Jackson (1917, p. 490, 498).
Mammal.-In 1942 T. F. Thompson found an incomplete mammal bone in the transition zone between the Culebra and Cucaracha formations at locality 110 onthe east side of the canal-the first Tertiary maminal to be found in Panamd. The following comments on this fossil and the drawings by 0. J. Poe reproduced as figure 2 are available through the kindness of R. A. Stirton, of the University of California.
The bone found by Mr. Thompson is the distal part (length 78 millimeters) of a metapodial of an ungulate of medium size. It was examined by H. E. Wood, 2nd, who thought it represents a rhinoceros similar to Diceratherium. G. G. Simpson doubted that it is a South American ungulate, but had no material for close comparison with the leontiniids. The apparent rhinoceros affinities seemed to be conclusive until late Miocene leontiniid foot bones, collected by University of California expeditions in
413788-57--4


Colombia, were available for comparison. This material indicates that the metapodial from the Canal Zone may represent a South American leontiniid or a North American rhinocerotid.

Despite a search in 1947 and 1949, no additional mammal remains were found at or near locality 110
Age.-Douvilld (1891, p. 499) and 1111 (1898, p. 195), relying entirely on lithologic similarity to lignitic strata in the Eocene of the Gulf states, suggested that the Culebra is Eocene. A review of other age assignments-Eocene, Oligocene, Miocene-would hardly be profitable. It may be pointed out, however, that DouvillS (1898, p. 591) and Bertrand and Zfircher (1899, p. 89, 90), evidently following his advice, thought that small orbitoids in strata that presumably represent the Culebra are reworked.
The fossils of the Culebra formation, including the Emperador member, have both Oligocene and Mioeette affinities. The orbitoids (three lepidocycline species of Lepidocclina) point to Oligocene. In fact, some paleontologists consider lepidocycline species to be decisive for an age not younger than late Oligocene. According to Vaughan's data, the corals favor correlation with the Anguilla formation of Anguilla, which contains no orbitoids. The mollusks also favor correlation with the Anguilla and other formations of the same age,


37


X







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


\~\~ :~" 1






~;;



\\ '~$N
K!

:,
~ ~-'



1



~ '!~





j





/1/
- ~,'/
77'
I ,72i /
-,
4' /1 ( i
Lj


317,


II

'ill I1~,III


I ~
~
It tttl
II

fffl

K H'~
ti,1 /


2











If I i/Ill!' ~
I \J)III~l

I'





~2( \ \

5


Figure 2.-Ungulate mctapodial from transition zone between Culebra and Cucaracha formations. Univ. Calif. Mus. Paleontology 37363, natural size. 11, 4. Lateral viewNs
2. Front view 3. Distal view
5. Posterior view


including the Tampa limestone of Florida, which also contains no orbitoids. None of the mollusks in the preceding list suggest species that are only of greater age than disputed Oligocene or Miocene, whereas Littorina aff. L. angulifera, Pachycrommium? cf. P. guppyi, and Turritella cf. T. subgrundifera suggest species that are only of younger age than disputed Oligocene or Miocene. Whether the Culebra formation is to be assigned to the late Oligocene or early Miocene is part


of the larger question of whether the Aquitanian stage of western Europe is late Oligocene or early Miocene, for the Culebra and correlated formations are the essential equivalent of the Aquitanian. It has long been recognized that the marine type Aquitanian of the Aquitaine basin contains an early Miocene fauna. The argument concerning the age of the Aquitanian centers on the Oligocene aspect of the mammalian fauna in nonmarine strata that are thought to be the equivalent


38


0









of the marine type Aquitanian. An early Miocene age for the Culebra formation agrees with the age assignment adopted by the Geological Survey for the Tampa limestone. That assignment for the Culebra, including the Emperador member, is adopted for the present report, instead of the late Oligocene(?) and early Mioeene age assignment recently used (Woodring and Thompson, 1949, p. 239).
CUCARACHA FORMATION
The Cucaracha formation crops out along and near the canal in the Gaillard Cut area and southeastward to Miraflores Lake. Its distribution is much like that of the underlying Culebra formation, but it is recognized at a greater distance from the canal than the Culebra. The name was proposed by MacDonald (1913, p. 569). Up to that time the strata constituting the Cucaraicha formation had been included in the Culebra. The type region is in the southern Gaillard Cut area. The site of the village of Cucaracha was on the east side of the canal between the continental divide and Paraiso. The maximum thickness of the formation is about 190 meters. The discontinuity at the base of the Cucaracha generally is sharp and marked by conglomerate, but in central Gaillard Cut a transition zone lies between the two formations. (See p. 35.)
STRATIGRAPHY AND LITHOLOGY
The Cucaracha formation is the most distinctive and the most uniform formation in the Canal Zone. It was involved. in the extensive slides in Gaillard Cut during excavation of the cut and during t period of several years after the canal was opened. Its physical properties were exhaustively investigated during the studies of the Third Locks project, carried out by the Special Engineering Division.
The principal constituent of the formation is massive generally grayish yellow green waxy highly slickensided bentonitic clay. Carbonaceous and lignitic clay, clayey siltstone containing yellowish gray calcareous concretions, tuffaceous clayey sandstone, and small-pebble conglomerate that has a tuffaceous matrix are minor constituents (Thompson, 1947a, p. 16-17). A bed of dacitic welded tuff is a useful and exact datumi plane. Its thickness ranges from 0.3 to 10 meters. Ii the type region of the Cucaracha it lies 85 meters above the base of the formation and 60 meters below the top (MacDonald, 1947, p. 9; Thompson, 1947a, p. 17). It is the only hard rock in the formation and looks much like a lava flow. In fact, it was described as a sill by Howe (1908, p. 231), as a flow by MacDonald (1913, p. 569), and was shown as a flow in MacDonald's structure sections (Natl. Acad. Sci., 1924, figs. 4, 5, op. p.


52). Later, however, it was found to be an aggloiieratic tuff (MacDonald, 1947, p. 9-10; Thompson, 1947a, p. 16). Hand specimens show feldspar crystals, flattened little lentils of dark clay, and greenish angular rock fragments. During the investigations of the Geological Section of the Special Engineering Division this bed of tuff was known as the ash flow. Description of thin sections of the tuff and a chemical analysis are presented on pages 54, 55. Chemical analyses of six samples of clay from the Cucaracha were published in the National Acadeiy of Sciences report on slides (Nat]. Acad. Sci., 1924, p. 54) and were reproduced by MacDonald (1947, p. 10). Both reports just cited also include descriptions of microscopic and other features of the clay (Natl. Acad. Sci., 1924, p. 54-66; MacDonald, 1947, p. 12-19, 65-70). No mineralogical study of the clay by tmodirn techniques has beeii undertaken.
FOSSILS AND ACE
The absence of marine fossils and the presence of plant debris in carbonaceous clay suggest that the bulk of the Cucaracha formation is noii1narine. The only plant remains recorded consist of wood (Berry, 1918). A few marine and brackish-water fossils have been found in the lower part of the formation: Anadara and Crassostrea in conglomerate and poorly preserved molds and impressions of Anadara, Lucina?, and Tellina? in carbonaceous clay (locality 122). The collection from locality 122 is the only collection now available.
In November, 1956, R. H. Stewart found the distal end of a femur in the Cucaracha formation, about 10 meters above the top of the welded tuff, at Contractors Hill, in the Gaillard Cut area at the continental divide. It was examined by R. A. Stirton, of the University of California, who reports (in a personal communication) that it may represent a North American rhinocerotid or a South American notoungulate. In other words, the uncertainty is the same as that for the metapodial from the trasition zone between the Culebra and Cucaraehia formations (p. 37).
The few fossils found thus far furiiish no reliable evidence concerning the age of the Cucarachia. It is assigned to the early 'Miocene because both the inderlying Culebra foriation and the overlying Panam formation are considered to be of that age. PANAMA FORMATION, INCLUDING 1A BOCA MARINE MEMBER AND
PEDRO MIGUEL AGGLOMERATE MEMBER
The Panama' formation is the youngest Tertiary forimation in the Gaillard Cut and Pacific coastal areas. It crops out in scattered areas in the central and southern Gaillard Cut area and more extensively farther southeast and east. It consists mostly of volcanic rocks, the youngest volcanic rocks in the Canal Zone. To the


GEOLOGY


39







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


west it grades into undifferentiated volcanic rocks and west of the border of plate 1 volcanism continued much later.
The marine strata constituting the La Boca marine member and the agglomerate making up the Pedro Miguel agglomerate member interfinger with each other and with the lower part of the tuff and generally finegrained agglomerate forming the Panama formation proper. All three were formerly given formation rank (Thompson, 1947a, p. 18-19, 20; Woodring and Thompson, 1949, p. 241-242). For the time being, however, member rank appears to be preferable for the La Boca and the Pedro Miguel.
The Panama formation was named by Hill (1898, p. 200-202). That the name was casual is indicated by the expression "so-called Panama formation" on page 206 in his publication. The formation was named for exposures along the water front in the city of Panama, which is considered the type area. The names La Boca formation and Pedro Miguel agglomerate were proposed by Thompson (1943, p. 16-18). The Miraflores Locks area has been designated the type region of the La Boca marine member (Woodring and Thompson, 1949, p. 241) and the Pedro Miguel area is the type region of the Pedro Miguel agglomerate member. The thickness of the formation is estimated to be at least 300 meters.
STRATIGRAPHY AND LITHOLOGY
The La Boca marine member extends farther inland than any other part of the Panama formation. It overlies the Cucaracha formation or interfingers with the upper part of that formation. Nevertheless, if the La Boca is correctly identified, it also overlaps the Cucaracha and Culebra formations and rests directly on the Bas Obispo formation. The member consists principally of silty or sandy tuffaceous mudstone, flaggy tuffaceous sandstone, calcareous tuffaceous sandstone, conglomerate, and coralliferous limestone. Agglomerate and tuff, presumed to represent tongues from the Pedro Miguel agglomerate member and the main part of the formation, respectively, are other constituents. The stratigraphic relations of these strata, most of which contain marine fossils, were not understood until the subsurface explorations of the Geological Section of the Special Engineering Division revealed evidence that they overlie the Cucaracha formation. The fine-grained. strata formerly were assigned to the Culebra formation, sandstone to the Caimito formation, and limestone to the Emperador limestone member of the Culebra formation. No satisfactory outcrop section showing both a considerable part of the member and its stratigraphic relations is known. For that reason the Miraflores Locks area has been designated the type region. In that area there are outcrops, and relations to the Cuca-


racha formation are shown by subsurface sections. The town of La Boca, which furnished the name, was located near the entrance to Balboa Harbor, but was abandoned in 1954. Though the La Boca member overlies the Cucaracha formation, the lower part of the La Boca evidently is the southward marine equivalent of the upper part of the Cucaracha formation in the area of maximum thickness of that formation. The maximum thickness of the La Boca member is about 185 meters.
Along and near the canal the La Boca member is represented principally by mudstone in both outcrop and subsurface sections. The mudstone is similar to that in the Culebra formation, but may be distinguished by the lower content of carbonaceous matter and the richer foraminiferal fauna of the La Boca. Locality 124, on the east side of the canal at canal station 1702, is the northernmost locality where such mudstone is now known to crop out along the canal. Core drilling, however, penetrated the La Boca farther north in a syncline on the west side of the canal.
Mudstone of the La Boca exposed in the canal excavation between Paraiso and Pedro Miguel Locks (locality 130), at the north end of Mariflores Locks, and south of those locks (Geological Survey locality 6009) was described by MacDonald as part of the Culebra formation (MacDonald, 1919, p. 533-534).
Fossiliferous calcareous tuffaceous massive sandstone of the La Boca is exposed in an abandoned quarry off old Gaillard Highway near Summit (locality 128). When the cuts along the present alinement of the Panama Railroad were fresh, MacDonald found fossils in similar but less massive sandstone in cuts north and south of Summit (localities 126 to 127b.) At locality 127b the sandstone is overlain by tuff that MacDonald identified as representing the Panama' formation. (See his data in description of locality 127b, p. 124.) Finegrained fossiliferous tuff and tuffaceous siltstone crop out at locality 132 near Red Tank, a village that has been abandoned since plate 1 was drafted. Flaggy tuffaceous strata, ranging in grain size from sandy siltstone to poorly sorted gritty sandstone, are exposed in a cliff at the mouth of Rio Masambi on the east side of the canal. These strata are considered part of the La Boca member. They are unlike any strata in the Culebra formation and, like the La Boca member elsewhere, contain molds of Acila cf. A. isthmica.
Cream-colored and gray coralliferous limestone of Emperador type at the base of the La Boca member overlies, and partly interfingers with, the Cucaracha formation on Gaillard Highway 400 meters northwest of the junction with Madden Highway (locality 129). Similar limestone on Rio Masambi, on the east side of the canal (locality 123), lies directly on the Bas Obispo formation and has a thickness of 35 meters, the greatest


40








known thickness for limestone of Emperador type. A view of this limestone is shown in plate 9. It was
-recently identified as the Emperador limestone member of the Culebra formation (Woodring and Thompson, 1949, p. 237), but is now thought to represent the La Boca member. It is in an area where the La Boca is known to be present, although no continuity with other La Boca rocks has been established. If the limestone is now correctly identified, the La Boca member overlaps onto the Bas Obispo formation. The strata in Gaillard Cut between canal stations 1720 and 1730, described by MacDonald as "light-colored tuff bed locally overlapping Culebra beds" may possibly represent overlapping La Boca (Natl. Acad. Sci., 1924, p. 52, fIg. 4). Limestone of the La Boca near Red Tank (locality 131) was referred by MacDonald to the Emperador member of the Culebra formation, and sandstone and agglomerate overlying the limestone to the Caimito formation (MacDonald, 1919, p. 534, "section at Bald Hill near Miraflores Locks"; for other locality data see p. 124). In fact, MacDonald used the section near Red Tank to define the Caimito formation and its stratigraphic relations to the Emperador limestone member of the Culebra formation (MacDonald, 1913, p. 569).
The Pedro Miguel agglomerate member is a lens of essentially coarse-grained pyroclastic rocks. In the Pedro Miguel area, the type region, these rocks overlie the Cucaracha formation. The lower part of the pyroclastic rocks, like the lower part of the La Boca marine member, apparently is the equivalent of the upper part of thick Cucaracha sections. Farther south the pyroclastics appear as a tongue in the lower part of the La Boca marine member. The pyroclastic rocks of the Pedro Miguel member, as described by Thompson (1947a, p. 18-19), consist chiefly of fine- to very coarse-grained agglomerate. Bedding and sorting are poor to moderately well developed. Fine-grained tuff is interbedded with the agglomerate. The thickness of the Pedro Miguel member is variable, but the maximum averages about 100 meters. Agglomerate of the Pedro Miguel in the Miraflores area was formerly considered part of the Las Cascadas agglomerate or was doubtfully referred to that formation (MacDonald, 1919, p. 533). Howe, however, realized that agglomerate near the continental divide rests on the Culebra formation (1908, p. 222-223). (The Cucaracha formation had not yet been differentiated.) Like MacDonald, he thought that agglomerate farther south near Corozal is of pre-Culebra age (Howe, 1908, p. 223).
Much agglomerate is known to be present in an unmapped area between Madden Highway and Curundu. It is not known, however, whether all this agglomerate represents the Pedro Miguel member, as shown on


plate 1, or what rocks other than aglomerate crop out in the area.
The Panama formation proper is made up of tuff, tuffaceous siltstone, tuffaceous sandstone, and agglomerate. They evidently represent nonmarine essentially fine-grained tuff and tuffaceous strata that interfinger with and overlie the La Boca marine member and the Pedro Miguel agglomerate member. The geologic map (pl. 1) suggests that in the Pacific coastal area the Panama formation proper overlaps part of the Caimito formation, but that relation needs confirmation. Tuff characteristic of the Panamtd formation is light gray, rhyolitic, and contains much pumnice and minute fragments of glass (Hill, 1898, p. 200-201; Howe, 1907, p. 116-117). Such tuff is exposed along the water front in Panamd and in street cuts in Diablo Heights. Similar tuff near Miraflores, now included in the La Boca marine member, was informally designated the Miraflores pumice by Hill (1898, p. 198-199), a name he suppressed on a later page (Hill, 1898, p. 206). Comparison of the volcanic constituents of the Panamd amtd Caimito formations may afford a basis for confirmintg or rejecting earlier correlations of tuff in the Panami formation with rhyolitic tuff along the canal north of the continental divide (Hill, 1898, p. 201; Bertrand and Zfrcher, 1899, p. 91; Howe, 1907, p. 117). The apparent overlap of the La Boca marine member of the Panamii formation across the Cucaracha and Culebra formations indicates that their correlation deserves further consideration. In the ineantime, however, it is not accepted.
FOSSILS AND AGE
The only available fossils were found in the La Boca marine member.
Smaller Foraminifera.-Smaller Foraminifera are fairly abundant in fine-grained strata. They represent a more open-sea marine environment than the meager fauna of the Culebra formation. M. N. Bramlette, who examined the outcrop sample from locality 124 and some subsurface samples, points out the abundance of Siphogenerina transversa. The type locality of that species (Geological Survey locality 6010, 130 of present report) is in strata of the La Boca member penetrated in the canal excavation between Paraiso and Pedro Miguel. Siphogenerina also is found in calcareous sandstone at locality 128. Both the type locality of Siphogenerina transverse and Geological Survey locality 6009 were assigned to the Culebra formation in Cushmaim's account of Canal Zone smaller Foraminifera (Cushman, 1918).
Larger Foraminifera.-The type locality of Lepidocyclina miraflorensis (locality 132a), a lepidocycline species, represents the La Boca marine member. It has been suggested that that locality is near the rail-


GEOLOGY


41







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


road tunnel north of Miraflores Locks (Woodring and Thompson, 1949, p. 241), but it probably is submerged by Miraflores Lake. Cole has recently described thin sections of specimens from the type lot (Cole, 1953a). He also identified and described Lepidocyclina parvula, also a lepidocycline species, and Miogypsina panamensis from locality 131a, MacDonald's locality near Red Tank.
Corals.-MacDonald found two species of corals in limestone at his locality near Red Tank (locality 131). Both were recorded by Vaughan from the Emperador limestone member of the Culebra formation and one from the Anguilla formation (Vaughan, 1919a, p. 209; Geological Survey locality 6256). The following corals, found in limestone at the base of the La Boca member at localities 123 and 129, were identified by J. W. Wells:

Corals from limestone at base of La Boca marine member of Panamd formation


[Identification by J. W. Wells]

Stylophora imperatoris Vaughan- _ -Stylophora macdonaldi Vaughan ------- ------_---Acropora saludensis Vaughan ..------ __Porites cf. P. douvillei Vaughan - -_------- _-Montastrea imperatoris Vaughan ------Montastrea costata (Duncan)------------


Localities
123 129
-- X
-- X

X X


According to Wells, all except one of the above species (or comparable species) occur in the Emperador limestone member of the Culebra formation and that species (Montastrea costata) occurs in the Culebra formation proper. Two are found in the Antigua formation and three in the Anguilla formation of the Leeward Islands.
Mollusks.-Though mollusks are widespread in the La Boca member, they are nowhere abundant and most of them are not well preserved. Crepidula sp. (locality 125), Neverita? sp. (locality 130), and Turritella cf. T. collazica (locality 123) are the only species in the families covered by chapter A of the present report.
Echinoids.-Limestone at the base of the La Boca member at locality 123 yielded an echinoid identified by C. W. Cooke as Clypeaster concavus?. That species occurs in the Caimito formation of the Rio Mandinga area and in both the Antigua and Anguilla formations of the Leeward Islands. According to Jackson, Clypeaster gatuni, a Gatun species, was found in limestone in a swamp north of Ancon Hill (Jackson, 1917, p. 491). The swamp is now filled, but limestone occuring in that region presumably is in the La Boca marine member.
Age.-The Panama formation was the first formation in or near the Canal Zone to be given an age assignment. Wagner thought that reddish conglomerate and fragmental rocks at Panama are Permian (Wagner, 1861, p. 6, 16). Though that opinion, of course, has not


been taken seriously, Hill was inclined to consider the formation pre-Tertiary (Hill, 1898, p. 202). Bertrand and Zircher (1899, p. 90-91), however, pointed outA that the tuff on the Pacific slope of the district to be traversed by the canal is younger than strata ("gres ligniteux") now referred to the Culebra formation, and Howe (1907, p. 117) came to the same conclusion.
Though the La Boca fossils and the Culebra fossils for the most part indicate somewhat different facies, they have essentially the same age significance: both have Oligocene and Miocene affinities. The La Boca member-and presumably the entire Panami formation-is not much younger than the Culebra formation. Like the Culebra formation, it is considered early Miocene. The entire succession above the Las Cascadas agglomerate (Culebra, Cucaracha, and Panama' formations) is thought to represent the early half of early Miocene time; that is, the disputed Oligocene or Miocene. If the Panami formation east of the Canal Zone does not include the equivalent of the Culebra formation, presumably there is a slight discontinuity between the Caimito and Panami formations east of the Zone.
GATUN FORMATION
The two remaining Tertiary formations to be described are found in the Gatun Lake and Caribbean coastal districts. The older of the two is the Gatun formation, well-known for its rich fauna. In fact, the fossils of the Gatun formation attracted attention at' an early date. When Blake traveled across Panama. in 1853 on his way to California to join one of the transcontinental railroad surveying parties, he collected a few Gatun fossils (Blake, 1857, p. 1). Two years later Newberry crossed Panama on the same mission and also collected some Gatun fossils, but left' no account of his observations. At about the same time another traveler briefly commented on fossils at Monkey Hill (now known as Mount Hope) but saw none at Gatun (Deck, 1855, p. 241). A search of books and magazine articles written by Californiabound travelers during and after the gold rush doubtless would reveal other accounts.
The Gatun formation was named by Howe (1907, p. 113-114). In Spanish orthography the name is Gatd'n. That name, however, was not the earliest for the formation. Hill had already used the names Monkey Hill formation and Mindi Hill beds (1898, p. 176, 180). Howe, indeed, used both Gatun formation and Monkey Hill formation in a structure section in the publication in which he proposed his name (1907, pl. 147), and in a later publication used only Monkey Hill formation (1908, p. 228). MacDonald's usage apparently established preference for Howe's name (MacDonald, 1913, p. 530). The type area is


42







the one described by Howe: from Gatun to Mount Hope (Monkey Hill of Howe's time). As a result of faulty paleontological information, Howe excluded the oldest strata near Gatun from the Gatun formation and grouped them with the Bohio formation (1907, p. 113). It is now known that the oldest outcropping part of the formation is not represented in the type region.
The outcrop area of the Gatun extends from Maria Chiquita, 20 kilometers northeast of Colon (pl. 1), to Rio Miguel, 50 kilometers southwest of Col6n (fig. 11), but much of that area has not yet been examined. The relations of the Gatun to the next older formation in the Gatun Lake and Caribbean coastal districts-the Caimito formation-are unknown. In the Canal Zone the contact between the two formations is covered by the waters of Gatun Lake and even before the flooding of the lake perhaps all of the contact was concealed by swamps. East and west of the Canal Zone, however, the Gatun presumably rests on the Caimito formation at outcrop localities, as shown on plate 1. So far as now known, no deposits of early Miocene age are included in the Caimito formation of the Gatun Lake area. The boundary between the two formations therefore is presumed to represent a discontinuity representing early Miocene time. Still farther east the Gatun formation overlaps the Caimito and directly overlies the Cretaceous(?) basement. At the west end of the outcrop area the upper part of the formation is interpreted as overlapping on the Caimito formation, not on the basement complex as previously surmised (Woodring and Thompson, 1949, p. 243).
The dip of the Gatun is low, between 5' and 10', and flattens out northwestward toward the coast. Nevertheless a water well at Mount Hope penetrated a thickness of 425 meters of Gatun strata without reaching the base of formation (Thompson, 1947a, p. 20). The total thickness is estimated to be at least 500 meters and perhaps a considerable thickness is concealed by overlap.
STRATIGRAPHY AND LITHOLOGY
Massive medium- to very fine-grained sandstone and siltstone are the chief constituents of the Gatun formation. They are somewhat calcareous, or marly, somewhat tuffaceous, and have a clay-like matrix. The sandstone contains numerous grains of black and greenish volcanic rocks and is practically a subgraywacke, as indicated by Boutan's (1880, p. 13) early account, the only description of the microscopic petrology so far published. Conglomerate and hard brittle very fine-grained tuff make up a small part of the formation. Basalt intrudes older formations in the


Gatun Lake area, but is not known to penetrate the Gatun.
The Gatun formation has been subdivided in various ways on faunal grounds (Woodring, 1928, p. 76-77; Olsson, 1942, p. 244-247; Thompson and Keen, 1946). The subdivisions adopted for the present report correspond to the three faunal zones proposed by Thompson and Keen. Though the subdivisions are based on faunal grounds, they are simply designated lower, middle, and upper parts, at least until the study of the fossils is completed. Both fossil collections and observations on the lithology, however, are scattered and eventually some other nomenclature may be found to be more satisfactory.
The lower part consists principally of medium- to very fine-grained sandstone. This part of the formation was unknown before the explorations of the Geological Section of the Special Engineering Division. In some exposures along the Transisthmian Highway and the road from the highway to Maria Chiquita, a basal conglomerate of variable thickness is present. It is most conspicuous along the Transisthmian Highway ihmediately south of Sabanita and is thin or absent along the road to Maria Chiquita. At locality 135 molds and impressions of marine mollusks were found in sandstone partings in the conglomerate: in the sandstone itself and in ferrugineous concretions. At some localities along the road to Maria Chiquita, sandstone is at the base of the formation and at others, where the base itself is not exposed, carbonaceous siltstone or mudstone, containing molds of marine mollusks, is close to the base. Fine-grained sandstone is exposed in cuts on the Transisthmian Highway between Sabanita and Cativa. Much of the sandstone, as at localities 136-138, contains numerous well-preserved fossils.
The middle part includes the best known strata: those at and near Gatun, including the strata excavated for the Gatun Locks and the uncompleted Gatun Third Locks. The three members recognized by MacDonald (1913, p. 570) and the strata he described later (1919, p. 542-543) are in the middle part. Though sandstone is the chief constituent, the middle part includes conglomerate, siltstone, and tuff. When dry the tuff is almost white and forms conspicuous outcrops in excavations. It was designated fullers earth by MacDonald.
The following section, described in a report by the Geological Section of the Special Engineering Division (Thompson, 1943a, p. 10-19, figs. 5-13 to 5-22) and by Jones (1950, p. 916-917, table 3), is exposed in the Gatun Third Locks excavation east of Gatun. The numbering of the units is that used by Thompson and Jones.


GEOLOGY


43







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


Section of strata in middle part of Gatun formation as exposed in
Gatun Third Locks excavation


[After Thompson and Jones]

12. Sandstone and siltstone
d. Massive very fine-grained silty sandstone; thin lenses of conglomerate (thickness a few cm) made up of pebbles of volcanic rocks. Contains leached shells and few carbonized plant remains_-------------------------c. M arly siltstone _____- -- -__----- _b. Clayey marly siltstone. Contains abundant well-preserved shells and some plant remains. Locality 155c _------a. Lens of medium- to very fine-grained silty
and marly sandstone_- ..-- _--- _-----11. Massive medium- to very fine-grained, silty and
marly sandstone. Contains abundant shells and fragments of carbonized wood. Shells arranged in layers and concentrated in pockets. Locality 155 represents units 11 a n d 1 2 _- -_ _ - _- _- _- ._- _10. Poorly sorted conglomerate, increasingly calcareous upward. Consists of pebbles of dense volcanic rocks (maximum length 10 cm) in matrix of medium-grained sandstone. Contains shells and bits of carbonized wood.
Locality 154 -------- -- _-_-_---- __-_-9. Coarse-grained tuffaceous sandstone, consisting
principally of grains of dark-colored volcanic rocks, quartz, and pumice. Uppermost 60 cm conglomeratic; thin lenses of conglomerate throughout. Contains a few shells, m ostly leached __- _- _- _- _..-_- _..---____-8. Sandy and silty tuff. Grain size decreasing
downward and pumice more abundant downward. Contains a few leached shells7. Hard, brittle, massive, very fine-grained tuff,
consisting chiefly of minute glass shards.
Contains rounded pieces of pumice (maximum diameter generally 5 cm)___..--___-6. Coarse-grained sandstone, upper part conglomeratic __-----_-..---_-_--- -- _5. Massive medium- to fine-grained, poorly sorted,
somewhat tuffaceous sandstone. Contains scattered basalt pebbles, leached shells, and bits of carbonized wood---_ -___ ---. --._-4. Medium- to very fine-grained tuffaceous sandstone, sandy tuff, and very fine-grained tuff in beds 15 to 90 cm thick. Increasingly fine-grained, tuffaceous, and pumiceoiis dow nw ard _--- _..__-- _- __-- _-- -- _-_3. Massive, medium- to very fine-grained somewhat marly sandstone. Glass shards and pumice fairly common in lowest 3 meters, decreasing upward. Contains scattered shells, echinoid fragments, and fragmentary carbonized and calcified plant remains.
L ocality 153a ..-_..-.-----------------2. Hard, brittle, massive, very fine-grained tuff_-_-


Meters


Section of strata in middle part of Gatun formation as exposed in
Gatun Third Locks excavation-Continued


[After Thompson and Jones]

1. Massive medium- to very fine-grained, silty to


so
m le


Me ter .1


mewhat marly sandstone. Contains nuerous shells, for most part more or less ached. Locality 153 ------------------- 31. 1

Thickness of section------------------- 151-156.5


7.9
3. 3 Units 1 to 4, inlusive, of the preceding section are shown in plate 10. The conglomerate forming unit 10 probably is the same bed as the conglomerate near 8. 4 Gatun described by Howe (1907, pp. 113-114; 1908, 1 5 pp. 228-229). In his 1908 account Howe was tempted
to select the conglomerate as the base of the Gatun formation (his Monkey Hill formation of that account), but his view was influenced by faulty paleontologic information. Unit 10 is stratigraphically not far from the base of the Gatun at Gatun Dam spillway as selected by Olsson (1942, p. 244-245). At all events his unconformity between the Gatun and Caimito for-


mations, as he now realizes (personal communication), is a minor discontinuity in the middle part of the Gatun formation.


6
Sandy and marly siltstone seem to be the principal
constituents of the upper part of the formation, at
least in the Mindi (localities 171-173) and Mount
Hope (localities 174-178) areas.
7. 2 Both upper and middle parts are represented west of the canal. Farther south-that is, west of Gatun Lake-the upper part evidently is overlapped by the 9. 1 Chagres sandstone and its Toro limestone member.
Collections of fossils west of the canal and west of Gatun Lake were made by A. A. Olsson during explora3.6-6 tions for the Sinclair Central American Oil Corporation in 1918, but his map and report are no longer
1. 2 available. Some of the localities at which fossils were
collected cannot be plotted on plate 1 and those that are plotted are located only approximately. Olsson's 11. Anomia zone west of Gatun Lake is considered part of the Toro limestone member of the Chagres sandstone, not part of the Gatun formation (Olsson, 1942,
p. 246-247).
3. No information is available concerning the Gatun formation between locality 170, west of Gatun Lake near Escobal, and the western end of the outcrop area, where the formation emerges on the coast, as shown in figure 3. Collections of fossils made by geologists of the Sinclair Central American Oil Corporation in 21. 3 1918 indicate that only the upper part of the Gatun 1. 8 is represented in the far western coastal area. That


44


r


3 6








GEOLOGY


80*30' 80*00'


101
P, Cocl del Norte
C


Bel6n TV

7 < Rio Paimea
> A
I I I A
<
<
< >7 V_ >< San
Crist6ba


Lagarto 208
180 Trh
185 Chila 179
184

T
P tao T

A .V 000A


I > D,> , V 1, > 'ATUN,<
<>A 'LAKE >
>A <
-V > <
>
NA A I A
>
Tv
1 17
>
> >
< > < A
>
I A < >
< <


ase from Panam6 sheet of American Geographical Society's map of Hispanic America



Scale 1:1,000,000
5 0

10 0


EXPLANATION




0 8 ] h T(,




Gatun formation 0 Undifferentiated volcanic and intrusive rocks


Contact
180
Locality where fossils were collected Figure 3.-Reconnaissance geologic map of Caribbean coastal part of Panamad irnmediatelywest of Canal!Zone.
Base from Panam0 sheet of American Geographical Society's map of Hispanic America.


interpretation, however, and the areal geology shown on figure 3 need confirmation. The matrix of the fossils consists of silty very fine-grained sandstone and sandy siltstone.
FOSSILS AND AGE

Sonaller Foraminifera.-Smaller Foraminifera from the Gatun formation were recorded by Cushman (1918). Marly siltstone in the upper part of the formation in the Canal Zone contains more species than those of Cushman's report.


Molluosk.-Mollusks are by far the most abundant and widespread fossils in the Gatun formation. The collections at the U. S. National Museum represent a collecting span of a century. In 1853 Blake collected three species described two years later by Conrad (1855, p. 18; 1857, p. 328, pl. 6, figs. 53-55). Only one of the fossils found by Blake is known to have survived: the type of "Gratelupia?" mactropsis [Lirophora mactropsis], a double-valve mold to which some inner shell material clings. Blake's form of locality citation is equivocal:


45


31*00'


00 80*30' 80


9*


1()


25 Miles

50 KilometerE






46 GEOLOGY AND PALEONI

"At Gatun, or Monkey Hill?, where we stopped for a few moments, I obtained several fossil shells from the embankment at the side of the road" (Blake, 1857, p. 1). He evidently meant he was not certain whether the place where the train stopped was Gatun or Monkey Hill, although that uncertainty seems strange. Two of the three species he collected (Lirophora mactropsis and Clementia dariena) are not known to occur at Monkey Hill [Mount Hope], whereas they do occur at Gatun. The preservation and matrix of the type of Lirophora mactropsis strongly suggests unit 1 of the section on page 44. There is no reasonable doubt that Blake picked up his fossils at Gatun. According to the locality data in Conrad's description of Newberry's fossils, Newberry on his trip two years after Blake's also collected at Gatun (Conrad, 1857a, p. 72). Conrad recorded five species, but Gabb added eight others, including the only cephalopod to be found in the Gatun formation (Gabb, 1881). Some of Newberry's fossils have been found recently at the Academy of Natural Sciences of Philadelphia.
Other Gatun fossils of the same vintage were collected at Monkey Hill (Mount Hope of present terminology) in 1857 by J. Rowell. Some of Rowell's specimens have early Smithsonian Institution catalog numbers (63916395), which were entered in 1880 under the locality "Monkey Hill, near Gatun." Most of them, however, have National Museum catalog numbers entered in 1893 under the locality "near Gatun." One of the latter series of numbers has the notation "collected in 1857." It is assumed that "near Gatun" should read "Monkey Hill, near Gatun." According to Dall, Rev. J. Rowell was an old collaborator of the Smithsonian Institution and a pioneer of 1849 in California (Guppy and Dall, 1896, p. 307). Rowell also collected fossils in the Dominican Republic. Unfortunately some of his specimens, including the types of Phos metuloides, Terebra bipartita spirifera, and Pecten scissuratus, are alleged to be from the Dominican Republic, but evidently were collected at Mount Hope. On the contrary, a few labeled "near Gatun" apparently were collected in the Dominican Republic.
The bulk of the collections at the National Museum was gathered during the period 1911-13 by MacDonald and Vaughan. Notable later accessions resulted from the field work of Olsson and other geologists of the Sinclair Central American Oil Corporation in 1918. The most recent collections studied for the present report are Thompson's made in 1942-43 and my own resulting from the 1947 field work for the present report.


0


LOGY OF CANAL ZONE

A total of 90 collections is being studied for the present report: 9 from the lower part of the formation, 58 from the middle part, and 23 from the upper part. On the basis of slight faunal differentiation, the collections from the middle part are divided into those from* an eastern area (east of the canal, 43 collections) and, those from a western area (west of the canal and west of Gatun Lake, 15 collections). On the basis of both: faunal and age differentiation, an eastern area in the Canal Zone (15 collections) and a western area, comprising the western coastal district (8 collections), are recognized in the outcrop area of the upper part. As shown by the data in the description of localities (p. 125-129), many collections, particularly from the" middle part of the formation in the eastern area, are, duplicates or virtual duplicates. Three collections contain more than 100 species: those from localities138a and 155 (both about 125 species), and locality 147b (about 110 species). The first two are among Thompson's collections from the lower and middle parts of the formation, respectively. The third, one of MacDonald and Vaughan's from the middle part, is especially rich in minute specimens, including 300 or', more of Teinostoma spermatia and about 200 microscopic shell tips of Turritella altilira.
The scattered publications describing mollusks of theGatun formation are listed on pages 5-10. The most important are those by Toula (1909, 1911), Brown and Pilsbry (1911, 1913), and Olsson (1922). Almost allthe large species that occur in the middle part of theformation have been described, but most of the minute species in that part, and many of both large and minute species in the lower and upper parts are described for the first time in the present report.
The available molluscan fauna is estimated to totalabout 350 species. In chapter A of the present report 46 species and subspecies are described and 4 others, not represented in the collections at hand, are recorded. The species included in chapter A are tabulated on page. 48. In that table "cf." in the locality columns indicates the presence of incomplete or poorly preserved materials that may or may not represent the form listed opposite in the species column. Likewise the designation "sp." in the locality columns means an unidentified incomplete or poorly preserved species that may or may not be the same as that in the species column. The designation "?sp." in the locality columns indicates thatthe genus is questioned. The columns labeled "Other. collections" list species or occurrences not represented in the collections at hand.








The table on page 48 includes two of the most characteristic species of the Gatun formation: Turritella altilira and T. gatunensis. It also includes species that have living relatives in the Pacific Ocean but not in the Caribbean Sea, and species that survived in the Pacific but not in the Caribbean Sea (Trochita trochiformis, Neverita reclusiana, and N. helicoides).
Echinoids.-Clypeaster gatuni, Encope annecteis, E. platytata, E. megatrema, and Schizaster panamensis w ere described by Jackson (1917).
Ostracodes.-Strata in the lower part of the Gatun formation at Cativa, for which the name Cativa marl was casually used, yielded 18 species and varieties of ostracodes (Coryell and Fields, 1937).
Age.-Age assignment of the Gatun formation was off to a good start when Douvilld (1891, p. 497-498) wrote that strata at Monkey Hill, Mindi, and Gatun are Miocene, and a few years later ventured the opinion that the strata at Monkey Hill are perhaps of Helvetian age, whereas those on the upper Chagres [Alhajuela sandstone member of Caimito formation] seem to be of Burdigalian age (Douvills, 1898, p. 592). Both age assignments are practically the same as those of the present time. Between publication of Douville's two reports, Dall beclouded the issue by maintaining that the strata at Gaten and Minidi are Eocene, and those at Monkey Hill Oligocene (Hill, 1898, p. 176, 180-181, 271-272, 273-274). As already outlined (Woodring and Thompson, 1949, p. 231), Dall was a victim of unfortunate circumstances so far as the Eocene part is concerned. One of Hill's collections was labelled Vacmos Vamos, though there is no doubt it was collected from the Gatun formation near Gatun (locality 158), apparently from strata near the base of the middle part; that is, it was labelled as though it represents the late Eocene or early Oligocene marine memberof the Bohio(?)formation. (See notationstcnder localities 40 and 158 on p. 115, 127.) Nevertheless Dall certainly would have been suspicious had lee arranged the collections according to Hill's field numbers, instead of arranging the real and alleged collections from Vamos Vamos biologically in one lot. The same mistake was made much later when an ill-advised early Miocene age was proposed for Hill's mixed fossils (Woodring, 1928, p. 76). All except a few of the alleged fossils from Vamos Vamcos have Hill's field number 17 on the specimens, in the vials, or on the labels written by Dall. Two lots bear the field number 18 (a Vamos Vamos collection, locality 40a), but 17 is written on the labels. One lot of Turritella altilira praecellens (USNM 135160) has 18 on the label and nothing but the catalog number in the vial. Regardless of numbering, the fossils from the Gatun formation may readily be sorted out, not onlyibecause the rock


cmatrix on microscopic examination is seen to be characteristic, but also because none of the species occurs at Vamos Vamos.
Dall's assignment of part of the Gatun formation to the Oligocene was the result of his conviction, first published in 1896 (Guppy and Dall, 1896, p. 303-304), that the Mioceee of the Caribbean region (and all except the very latest of the Miocene in southeastern Uniited States) really is upper Oligocene. Toula justly protested against an early Tertiary age for the Gatun formation, but went too far in the opposite direction in claiming that the Gatun (that is, the middle part of the formation) is of late Miocene or even Pliocecne age (Toula, 1909, p. 737). For many years the Gatun formation has been considered middle Mioceee. A discussion of the age would be premature until the numerous mollusks are identified. Preliminary exacination suggests that in the Canal Zone the formation represents the entire span of middle Miocene timeessentially the equivalent of the Cercado and Gerabo formations of the Dominican Republic-and that the upper part in the western area, west of the Canal Zone, is late Mfiocene.
Vf,10CENE SE RIFS
CHANGES SANDSTONE, INCLUDING TORO LIMESTONE MEMBER
The youngest Tertiary marine formation, the Chagres sandstone, overlies and partly overlaps the Gatun formation. The outcrop area lies entirely west of the canal, extending from the Canal Zone soctlwestward along the Caribbean coast to a locality between Rio Indio and Rio Migecel, about 45 kilometers southwest of Col'n (fig. 3). Meluch of the outcrop area, except in the Canal Zone and along the coast, still remains to be examined. Calcareous strata at the base of the formation throughout most of the outcrop area in the Canal Zone constitute the Toro limestone member.
The name Chagres sandstone was proposed by MacDonald for the sandstone forming the hills that overlook the coast from Toro Point to the mouth of Rio Chagres (MacDonald, 1919, p. 532). The saccdstone is so massive that estimates of thickness are uncertain. MacDonald's estimate of 1,000 feet (300 meters) or more may be excessive.
Tihe Toro limestone member also was named by MacDonald, who designated it a separate formation (MacDonald, 1915, p. 26). Toro Point was specified as the type locality. Earlier MacDoniald (1913, p. 570) used the informal name Caribbean limestone for this unit. The average thickness of the Toro is about 40 meters (Thompsoe, 1947a, p. 21).
STRATIGRAPHY AND LITHOLOGY
The Toro limestone member is a local basal calcareous deposit of variable thickness. It consists princi-


GEOLOGY


47









GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


C-1 ~


"Margarites" sp-Calliostoma (Leiotrochus) eremum Woodring, n sp -_____ -__ -_ - - -- ______Turbo (Marmarostoma) aff. T. castaneus Gmelin_-..
Tricolia? syntoma Woodring, n. sp Neritina (I7itta?) cf. N. virginea (Linn6) Teinostoma (Idioraphe) spermatia Woodring,
n. sp.---------------_-....-...--angulatum trochalum Woodring, n. subsp.
(Aepystoma) andrium Woodring, n. sp._(Pseudorotella) pycnum (Woodring)------stemonium Woodring, n. sp------------(Diaerecallus) sychnum Woodring. n. sp__. Anticlimax (Anticlimax) gatunensis Pilsbry
and Olsson -- __-_ -_ ----
(Subclimax) teleospira teleospira Pilsbry andO lsson -_ - _____________-hystata Woodring, n. subsp..
Cyclostremiscus (Ponocyclus) pentagonus
(G abb) -------. -- --_--
Solariorbis (Solariorbis) strongylus Woodring,
n.sp------------------------(Hapalorbis) hyptius hyptius Woodring, n.
sp. and n. subsp..-...........---anebus Woodring, n. subsp
Episcynia megalia Woodring, n. sp -.. "Alvania" aff. "A." epulata (Pilsbry and
Johnson)
Rissoina (Phosinella) oncera Woodring, n.
sp --------------------------Xenophora delecta (Guppy) --Crepidula cf. C. maculosa Conrad -------p lan a S ay --.. ------------------------Calyptraea centralis (Conrad)--Trochita trochiformis (Born)---Crucibulum (Crucibulum) chipolanum Dall
(Dispotaea) springvaleense Rutsch Cheilea princetonia Brown and Pilsbry Natica (Natica?) bolus Brown and Pilsbry(Naticarius) canrena (Linn6)
stenopa Woodring, n. sp-----------Stigmaulax guppiana (Toula) -----------Tectonatica agna Woodring. n. sp -------Polinices canalizonalis (Brown and Pilsbry)
brunneus subclausus (Sowerby) -stanislas-meunieri Maury ----------Neverita (Glossaulax) reclusiana xena Woodring n. subsp-----------------(Hypterita) helicoides (Gray) ----------Sinum gatunense (Toula) -------------euryhedra Woodring, n. sp---------gabbi (Brown and Pilsbry)------------Turritella (Torcula) altilira Conrad, s. 1 .-..altilira altilira Conrad_-. .------------
altilira praecellens Pilsbry and Brown abrupta Spieker------------------matarucana Hodson ...-------gatunensis gatunensis Conrad.-----
rhytodes Woodring, n. subsp.-...-mimetes Brown and Pilsbry..-......tifastigata Nelson-----...---...-.......-


X

- i


X


X


--

--

X
_-


X


X


X

X
X
--








X
X
X
X


Mollusks from Gatun formation
[For explanation of symbols see p. 46]

Localities

Middle part Lower part Eastern area


X
X



X

X


X


X
X


X

X
---







..X

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-
X


a a
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X


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--

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X

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X X

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X --


--X
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- -
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--..



--

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--



--

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---
sp.
----


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X


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-

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--
--

--
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---


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cf.



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a


.0


?sp.


x


X



X


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--




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X
X

-I


--

---
X .---


C'.


X


X

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X






X

x
x
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--


x

X


cf.


--
--
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t-

?sp


X


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--
--
--
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'0


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X1 X X


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--


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---


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X



?


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cf.


----


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-- -- --- --- -- - - - - - _


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48


V


F _I..- -- F -.. -- -- I--- ---X X


-- --- --- ---


X.


-- --- ------ --- --- --- --- ---


--
---


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( Trochidae to Turritellidae)






Middle part Eastern area












X

--- --- -- ---- -- --- -- -- -- -- --


. ?sp.


-- -- --- ----X6 X X6 X -X --?I > > >-- -. ------X --


GEOLOGY



[For explanation of symbols see p. 46]

Localities


Upper part

Western area Eastern area












-- --- -- -- - -- - -- -- -- -- -- --- -- -- --- --- --x

X~- -- ---- - -- --



-- - - - - --- -- --I - - - -- -- - - -- X --


X6 -











---


X>


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49











Western area w000 6666









- - --- -- --
sp.















-- - -- -- X







- --- ---- --- --- - ---- -- -- - -.. ,










X X X X X ?
















x X X X X


?Sp. sp.


x


X


X


?


-








GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


pally of lime-cemented coquina made up of small fragments of barnacles, shells, echinoid spines, and corals (pls. 11, 12). Barnacle fragments predominate at many localities and cross-bedding is common. Lenses of medium- to coarse-grained sandstone occur in the coquina. Descriptions of outcrops of the Toro have been published by MacDonald (1919, p. 544-545) and Olsson (1942, p. 246).
The Chagres sandstone proper is made up of massive generally fine-grained sandstone and some siltstone (pl. 13). Unlike the Gatun formation, the Chagres is not known to include conglomerate or tuff, and the sandstone itself contains less volcanic material than sandstone of the Gatun.
FOSSILS AND AGE
Mollusks.-A few molds of mollusks from Olsson's Anomia zone are included in the families covered by chapter A of the present report: Calliostoma? sp. and Turritella gatunensis? from locality 194; Turritella altilira s. 1. from locality 195; Turbo aff. T. castaneus, Turritella gatunensis?, and Turritella mimetes? from locality 195. Olsson's Anomia zone (Olsson, 1942, p. 246-247) appears to be part of the shallow-water calcareous deposits forming the overlapping Toro limestone member of the Chagres sandstone rather than part of the Gatun formation.
A new species of Calliostoma, C. metalium (localities 206, 206a), an unidentified mold of Crucibulum (locality 201), and Stigmaulax guppiana (locality 208) occur in the Chagres sandstone proper. The mollusks of the Chagres sandstone proper, unlike those of the Toro limestone member, indicate deposition in water of moderate depth.
Echinoid.-A large species of Clypeaster, found in the Toro limestone member at locality 196 (Olsson's Anomia zone), is identified by C. W. Cooke as C. aff. C. bowersi. C. bowersi occurs in the Imperial formation of the Colorado Desert, of disputed Miocene or Pliocene age (probably late Miocene).
Age.-The Chagres sandstone is close to the border between Miocene and Pliocene; it has been assigned to both series. Preliminary examination of the mollusks suggests early Pliocene, despite the presence of a few Gatun species, such as Stigmaulax guppiana, and of other species that have Gatun affinities.
PLEISTOCENE SERIES
STRATIGRAPHY AND LITHOLOGY
Pleistocene marine deposits occur at altitudes of a few feet above sea level and in the seaward part of buried valleys are interbedded with swamp and stream deposits. Swamp and stream deposits filling buried valleys extend as far inland as Gamboa on the Caribbean side of the Canal Zone and as far as Miraflores Locks on


the Pacific side (Thompson, 1947a, p. 22). Black organic muck is the most widely distributed type of deposit. In fact, the geologists of the Geological Section of the Special Engineering Division used the in- a formal designations Atlantic muck and Pacific muck for the Pleistocene deposits (Thompson, 1947a, p. 22). According to Thompson's description, much of the black muck represents swamp deposits and is a mixture of silt, very fine-grained organic debris, and partly carbonized wood, stems, and leaves. Layers of marine fossils are found in black organic silt and calcareous mud containing plant matter. They were encountered at the north end of the excavation for the Gatun Locks and in ditches in swamps north and east of Mount Hope (Brown and Pilsbry, 1913, p. 493-494; MacDonald, 1919, p. 544). Brown and Pilsbry casually used the name Mount Hope formation, which they attributed to W. B. Scott, for Pleistocene strata near Mount Hope (Brown and Pilsbry, 1913a, p. 493).
FOSSILS AND AGE
Corals.-Corals in collections from localities near Mt. Hope have been listed by Brown and Pilsbry (1913a, p. 497) and Vaughan (1919b, p. 563). They evidently represent reef-flat species.
Mollusks.-A few new species of mollusks were described by Dall (1912, p. 1-6) and Brown and Pilsbry (1913a). Brown and Pilsbry listed the species in the two collections they studied. The few species in their collection from the north end of the Gatun Locks excavation indicate brackish water and the deposits themselves point to deposition in a swamp. The depositional environment of the large number of marine species in their collection from a locality near Mount Hope, and in MacDonald's collections from the same region, is uncertain on the basis of published data.
Contrary to Dall's statement (1912, p. 1), MacDonald's collections from the Caribbean side do not contain any species now living along the Pacific side.
The Pleistocene mollusks are not described in the systematic part of the present report.
Age.-With the exception of the new species of mollusks, the identified fossils from the Pleistocene marine deposits on the Caribbean side of the Canal Zone are known to be living in the Caribbean Sea. Dall, and Brown and Pilsbry realized that their new species may be found to be living when the fauna along the Caribbean coast of Panama is better known. The Pleistocene deposits-at least the marine deposits-probably are of late Pleistocene age, but may be too old for radiocarbon dating.
CORRELATION OF TERTIARY FORMATIONS IN DIFFERENT AREAS
Correlation of the Tertiary formations in different areas and age assignments, as adopted in the present


50










PALEOCENE EOCENE OLIGOCENE MIOCENE PLOCENE CRETACEOUS(?)

Caimito
ormation


or0 a0'_ton









































AflIIQto







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


report, are shown in figure 4. Some features cannot be shown properly in figure 4: the age assignment for the Bas Obispo formation and Las Cascadas agglomerate is Oligocene(?), despite the seemingly definite position on the chart; the age assignment for the marine member of the Bohio(?) formation of the Gatun Lake area is late Eocene or early Oligocene, not late Eocene and early Oligocene as the chart suggests.
The correlations differ only in some minor details from those of Woodring and Thompson in 1949 (fig. 2). The following changes have been made in age assignments: Gatuncillo formation, middle and late Eocene instead of late Eocene; Bohio formation of all five areas, early and late Oligocene instead of only early Oligocene (except in Pacific coastal area, which was not shown in the 1949 chart); Culebra formation, including Emperador limestone member, early Miocene instead of late Oligocene(?) and early Miocene; upper part of Gatun formation in western area (not shown in figure 4), late Miocene, instead of middle or late Miocene; Chagres sandstone, early Pliocene instead of late Miocene or early Pliocene. Though the Bas Obispo and Las Cascadas formations are still considered Oligocene(?), they are given a greater probable time range in the Oligocene.
Some of the proposed correlations are unsatisfactory. There is no satisfactory faunal or lithologic correlation between Madden basin and the Gaillard Cut area. On the contrary, at least parts of the Caimito formation of the Quebrancha syncline, the Gatun Lake area and the Pacific coastal area can be correlated with the lower part of the Caimito of Madden basin on fairly satisfactory faunal grounds. Plate 1 shows at a glance that Gaillard Cut and the Pacific part of the canal are close to the eastern border of a pile of volcanic rocks. Madden basin, the Quebrancha syncline, and the Gatun Lake area are farther seaward in the marine basin. The coarse pyroclastic rocks and flows of the Bas Obispo formation and Las Cascadas agglomerate, and the coarse pyroclastic rocks in the Panama formation represent seaward extensions of volcanic rocks from the volcanic pile. In Madden basin and the Quebrancha synchne such rocks are much thinner and are found only in the volcanic member of the Bohio formation and the pyroclastic-clay member of the Caimito formation. Pyroclastic deposits in the Gatun Lake area are of much finer grain than in Gaillard Cut. Tuffaceous debris is present in the Tertiary formations of all the area, but is more dominant in the Gaillard Cut area and the Pacific part of the canal than in Madden basin, the Quebrancha syncline, or the Gatun Lake area. The Cucaracha formation, for example, consists almost entirely of altered volcanic ash.
The lack of studies of the pyroclastic rocks and the


tuffaceous constituents of other rocks is the most serious deficiency in present knowledge of the geology of the Canal Zone and adjoining parts of Panamd. Such studies are likely to yield clues to correlations of the formations that may be more convincing than the faunal correlations.
IGNEOUS ROCKS
The following brief account of the igneous rocks is based principally on MacDonald's manuscript on the geology of Panamd mentioned on page 4. Much of the original manuscript, including some pages of the part dealing with the igneous rocks, is not preserved and his rock specimens and thin sections are no longer available. MacDonald's 1915 publication (p. 27-30) contains more data on the igneous rocks than his other publications.
The igneous rocks may be divided into two age groups: Cretaceous(?) and Tertiary. That classification embodies the chief addition to MacDonald's treatment.
CRETACEOUS(?) VOLCANIC AND INTRUSIVE ROCKS
Altered basaltic and andesitic lavas are the most common rocks in the basement complex, at least along the Transisthmian Highway and the pipe-line road in the eastern part of the Canal Zone. Two samples from the eastern part of the Canal Zone were examined by W. S. Burbank, who reports that the rocks are similar in texture and composition to the basaltandesite rocks of the Southern Peninsula of Haiti (Woodring, Brown, and Burbank, 1924, p. 320-330). Chlorite, calcite, and a little epidote are the principal alteration products in the two samples.
Basalt containing unaltered olivine is exposed on Quebrada L6pez (between Sabanita and Rio Agua Clara) at the Transisthmian Highway bridge. According to R. H. Stewart, similar olivine-rich basalt crops out in an extensive area northeast of the highway.
Andesite at Porto Bello-the colonial settlement 35 kilometers northeast of Col6n-is presumed to be part of the basement complex. As described by MacDonald, the rock is dark. Under the microscope it is markedly porphyritic and the phenocrysts are andesine, labridorite, bronzite, and some augite. The groundmass is largely glassy, but contains some minute crystals of plagioclase. This rock was used for concrete in the construction of Gatun Locks and great slabs were quarried for armoring the Limon Bay breakwaters.
The Cretaceous(?) lavas are intruded by dioritic rocks and dacitic porphyry. Though no debris from these intrusive rocks was noticed at the few localities where conglomerate of the Gatuncillo formation was observed, they probably antedate the Gatuncillo


52






GEOLOGY


formation and probably are of late Cretaceous, Paleocene, or early Eocene age. Cobbles of granodiorite, found by MacDonald in the gravels of Rio Cbagres and in conglomerate of the Bohio formation, presumably represent a group related to the Cretaceous(?) dioritic rocks.
TERTIARY VOLCANIC AND INTRUSIVE ROCKS
Though Tertiary lavas are found east of the canal and are widespread west of the canal, most of the Tertiary igneous rocks described by MacDonald and selected by him for chemical analysis were obtained from intrusive bodies.
GRANULAR INTRUSIVE ROCKS
Quartz diorite.-Cocovi Island, a small island in Panamn Bay west of the entrance to the canal, was found by MacDonald to be made up of quartz diorite porphyry. The rock is light gray but weathers almost white. It is markedly porphyritic, the phenocrysts, up to 6 millimeters in diameter, consisting of andesine, andesine-labradorite, some quartz, and a little orthoclase. Some of the feldspars are partly saussuritized. The ferromagnesian minerals are highly altered and for the most part unidentifiable; a few outlines of hornblende crystals were recognized. Though the finely crystalline groundmass is somewhat cloudy and altered, it seems to consist of plagioclase and shreds of ferronagnesian minerals. Magnetite, apatite, and chlorite are found in the rock. A chemical analysis of the porphyry is included in the table on page 55 (analysis 1).
Augite quartz diorite forms Point Farfan, on the west side of the Pacific approach to the canal at the ferry terminus opposite La Boca. At Point Farfan, like on Cocovi Island, MacDonald obtained, by blasting, rock that proved to be considerably altered, although of fresh appearance. The quartz diorite at Point Farfan is gray and weathers light gray. In hand specimens it is slightly porphyritic and the groundmass is granular and almost medium grained. In thin sections andesine and somewhat altered augite are conspicuous. Quartz is present in small irregular masses, some of which appear to be secondary. Many small shreds of highly altered indeterminable ferromagnesian minerals were observed. Magnetite and apatite are accessory minerals and chlorite is the chief secondary mineral. The rock was analyzed and the results of the analysis are presented in the table on page 55 (analysis 2).
Dacite.-The rock forming the Ancon Hill stock (between Ancon and Balboa), as well as Naos Island and Culebra Island in Panama Bay, was described as rhyolite by Howe (1908, p. 230-231) and MacDonald (1915, p. 28-29). In his manuscript MacDonald points out that although the rock has the appearance of rhyolite and some thin sections show as much quartz as shown


53


by many riyolites, the chemical analysis and additional microscopic examination show that it is dacite.
The dacite at Ancon Hill is light gray acd weather to a light creamy color. As described by MacDonald, it has a fine-grained texture and some lathlike phenocrysts of plagioclase, the largest of which have faces measuring about 1 by 5 millimeters. In thin section the rock shows flow structure, particularly around the phienocrysts, which consist principally of andesine and some albite. Quartz in irregular grains, some augite, and a few small greatly altered needles of hornblende are present. The phenocrysts are widely scattered and grade in size into the coarser particles of the groundmass. Though the groundmass is somewhat cloudy and altered, it consists principally of perthitic aggregates of orthoclase and plagioclase and some quartz and feldspar intergrowths. Accessory minerals, in order of decreasing abundance, are magnetite, ilmenite, and apatite. A considerable amount of chlorite is present and scattered patches of an unidentified light yellowish secondary mineral show in the groundmass. (See analysis 3, p. 55.) W. S. Burbank suggests that MacDonald's description and the chemical analysis indicate that the rock is considerably altered, principally by processes allied to albitization. During the construction of the canal a quarry on the west face of Ancon Hill, at a locality now known as Quarry Heights, furnished great quantities of this dacite for use in concrete in the construction of Mirafiores and Pedro Miguel Locks.
The stocks of porphyry between the canal and Madden basin, northeast of Gaillard Cut, include dacite porphyry, according to geologists of the Geological Section of the Special Engineering Division. The porphyry intruding the Gatuncillo formation in the Rio Casaya area (locality 38), for example, is dacite porphyry. The borders of this stock and the intruded rocks are slightly mineralized and socee mining operations were carried on many years ago, as described on p. 59. MacDonald thought some of the rock in this area probably is granodiorite, but he found nothing suitable for microscopic examination.
Diorite.-A minor faces of the quartz diorite at Point Farfan is described by MacDonald as quartz-bearing gabbro. W. S. Burbank, however, points out that MacDonald's description of the mineralogical composition and the chemical analysis indicate a classification near diorite. The rock is dark gray, medium-grained, and equigranular. The principal minerals, arranged in approximate order of relative abundance, are andesine, augite, and oligoclase. Quartz in small irregular patches is a minor constituent, which W. S. Burbank suggests may be secondary. Accessory magnetite, apatite, and ilmenite are present. Chlorite is found ice the rock and some of the feldspars show slight saus-






GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


suritization. W. S. Burbank points out that the soda content of the analysis of this rock on page 55 (analysis 4) is slightly high for normal diorite and suggests that the alteration recorded by MacDonald may indicate weak albitization.
Andesite.-Andesite porphyry forms some of the stocks in the area between the canal and Madden basin. A small stock of hornblende andesite, characterized by conspicuous needles of hornblende, is being quarried along the road between Miraflores Lake and the Transisthmian Highway.
DIKE ROCKS
Andesite.-Andesitic dike rocks that cut the Las Cascadas agglomerate are mentioned by MacDonald.
Basalt.-Dikes and small irregular intrusive bodies of almost black rocks, all grouped as basalt, are widely distributed southwestward from the southeastern part of the Gatun Lake area and the southern part of Madden basin. The irregular intrusive bodies form hills; in fact, most of the high hills in the southeastern part of the Canal Zone are formed by intrusive or extrusive basalt.
Basalt obtained from dikes at 10 localities, for the most part in Gaillard Cut, was examined by MacDonald. These rocks are very dark and fine-grained. Labradorite, andesine, and augite are the principal constituents among the larger crystals. Some of the rocks also contain enstatite and a little biotite. The groundmass is made up of laths of plagioclase and grains of augite, but generally includes a little glassy material. Magnetite and ilmenite are the chief accessory minerals. Some chlorite and a few patches of serpentine -possibly an alteration product of olivine-are present.
Basalt from a dike on the Panama Railroad 3 kilometers northwest of Monte Lirio was selected for chemical analysis. (See table, p. 55, analysis 5.) As described by MacDonald, the rock is of coarser texture than the usual basalt in the Canal Zone and its feldspars are more calcic. Hand specimens show crystal faces of pyroxene that shine with a resinous luster and have a maximum diameter of 4 millimeters. Under the microscope the largest phenocrysts are seen to be augite. The feldspar crystals, slightly in excess of the ferromagnesian minerals, are for the most part labradorite and some of them are zoned. A little andesine is present. Augite occurs in granular aggregates as well as in phenocrysts. Magnetite, apatite, some ilmenite, and a few small grains of zircon are present. Secondary minerals consist of numerous patches of iron oxide(?), some serpentine that may be an alteration product of olivine, and a few small patches of chlorite. Some of the feldspar crystals are partly saussuritized and in zoned crystals the alteration is zonally selective. This


rock was quarried for use in facing the water-level part of Gatun Dam.
VOLCANIC ROCKS AND TUFF
Dacite.-Dacitic glassy lava from the Las Cascadas agglomerate is included in the rocks selected for chemical analysis (see analysis 6, p. 55). According to MacDonald's description, the glassy lava forms the matrix of thin flow breccia. The brecciated fragments enclosed in the glassy matrix consist chiefly of pyroclastic rocks of the Las Cascadas. Some of the glassy lava contains elongated gas cavities drawn out in the direction of flow.
The hard dacitic tuff in the Cucaracha formation, mentioned in the description of that formation, was also analyzed (analysis 7, p. 55). Thin sections of the tuff were examined by W. S. Burbank and R. L. Smith, who found it to be a welded tuff. The glassy base consists of compressed glass shards, for the most part partly or entirely altered to clay. Some of the plagioclase (andesine-labradorite) crystals are euhedral; others are fragmental. Decomposition products of a few unidentifiable ferromagnesian minerals are recognizable and the rock has a few veinlets of calcite. Fragments of finely crystalline lavas of varying composition are scattered through the tuff. The dark little lentils, conspicuous in hand specimens, consist of saponite (a clay mineral of the montmorillonite group), evidently an alteration product of compressed pumice lapillae.
Andesite. -MacDonald mentioned andesitic flow breccias and dark coarse-grained andesitic flows in the Las Cascadas agglomerate.
Basalt.-Some of the basalt in the southern part of the Canal Zone consists of remnants of flows and the undifferentiated volcanic rocks in the southwestern part of the map area include much basaltic lava.
A flow remnant capping Gold Hill, which forms the continental divide on the east side of Gaillard Cut, is described by MacDonald as dark fine-grained basalt. The larger crystals consist of feldspar, mostly labradorite, and augite. Augite also occurs as grains and irregular aggregates. The groundmass is distinctly crystalline, though very fine-grained. It has about the same composition as the larger crystals. Small grains and irregular aggregates of magnetite, some apatite, and a little ilmenite are scattered through the rock. Epidote in light and dark yellow irregular patches fills cracks in broken feldspars and occurs as cloudy masses in the interior of some feldspar crystals. The thin sections show no olivine, but a light yellow secondary mineral may represent altered remnants of olivine. A chemical analysis (No. 8) of this rock is included in the table on page 55.


54








GEO

CHEMICAL COMPOSITION
The chemical analyses of some of the rocks described in the preceding paragraphs are included in MacDonald's manuscript. As noted in the explanatory matter following the table of analyses, they have already been published in the Geological Survey's Bulletin 591. Missing pages of the manuscript may contain descriptions of the "andesitic rock near Empire" and the 'lava near Las Cascadas", analyses of which were published


in Bulletin 591. The norms of the analyzed rocks were calculated by MacDonald.
Some abnormalities in mineralogical composition resulting from various degrees of albitization probably account for the high soda and low lime content of some of the rocks, particularly the dacites (analyses 3, 6). The low potash content is typical of many similar rocks in the Caribbean region.


Analyses of igneous rocks and tuff from Canal Zone [Analysts: 1, 2, 6, 7, R. C. Wells; 3, 8, George Steiger; 4, 5, W. C. Whmeler]

Granular intrusive rocks Dike rock


Si02 -A20 -FeG0
Feo
A1g0 -- CaO -N120 K20 _ H20 --
H20- -Ti 2-C02 -- --P205 -_-

Cl -_ _. S _--- _----C r20 3_ _-_--_-MnO ----BaO---__-

Total-


63. 51 18. 07 2. 01 2. 18 2. 19 5. 14 4. 08 88 1. 07
.60 33
None
19
-----_-
.01 .01

06 03

100. 36


57. 39 69. 20 15. 84 15. 00 2. 38 1. 57 5. 96 1. 83 2. 41 69 5.24 1. 88 5. 23 5. 87 84 1. 81 1. 09 .90 1. 74 .67 1. 35 .52
Trace None .68 .10

.05
.01
_-------_.18 15
.02 --100. 41 100. 19


51. 72 15. 38 3. 35 7. 91 4. 38 7. 84 4. 37 .47 .56
2. 00 1. 67
None .49 03
12

None 16


100. 45


5


48. 23 14. 69 4. 49 5. 85 6. 73
12. 12 2. 55 1. 49 1. 50 .98 1. 00
Trace 46 05 09

06 17


100. 46


Volcanic rocks and tuIf

6 7 62. 23 65. 17


15. 22 2. 08 3. 98 1. 19 3. 79 3. 71 1. 52 2. 57

96 32






06


100. 57


14. 95 2. 04 1. 52 75 3. 10 5. 08 1. 26 8. 94 59
Trace 04


100. 50


8


51. 04 17. 34 2. 88 7. 33 5. 50 9. 79 2. 88 .53 96 72 1. 32
None
25


13


100. 67


I Shows a trace Of V203. 2 Shows traces of Zro02, F, and V2.

1. Quartz diorito porphyry, Cocovi Island, Panan Bay. Clarke, F. IV., Analyses 5. Basalt, Panamna Railroad, 3 ki northwest of Mtonte Lirio. Bull. 591, p. 214, of rocks and minerals from the laboratory of the U. S. Geol. Survey. U. S. Geol. analysis Q. Survey Bull. 591, p. 214, 1915, analysis 0. 6. Dacitic glassy lava in Las Cascadas agglomerate, Gaillard Cut. Bull. 591, p. 213,
2. Augite quartz diorite, Point Farfan. 1ull. 591, p. 214, analysis N. analysis E.
3. Dacatic, Ancon 5ill. Bull. 591, p. 213, analysis A. 7. Dacitic tuff in Cucaracha formation, Gaillard Cut. Bull. 591, p. 213, analysis B.
4. Diorite, Point Farfan. Bull. 591, p. 214, analysis P. 8. Basalt capping Gold Hill, Gaillard Cut. Bull. 591, p. 213, analysis G.


55


LOGY


22


f
1








GEOLOGY AND PALEONTOLOGY OF CANAL ZONE Norms
[Cross-Iddings-Pirsson-Washington classification]


Q uartz __.__-_._Orthoclase _-__--A lbite -__-_-_-Anorthite _Corundum Diopside
Hypersthene Olivine M agnetite _-_-.-Ilm enite__- ..____A patite____- _____-


1


22. 26 5. 00 34. 58
24. 74 1. 22

6. 06

2. 78 .60 .31


8.
5.
44. 20.


81 12. 63

3. 48 2. 58 1.55


Symbols: (1) 1.4.3.5, amadorose; (2) II.5.3.5, beerbachose; (3) tonose; (6) 1.4.3.4, yellowstonose; (8) 11.5.4.4-5, hessose.

AGE

The Bobio formation of the Quebrancha syncline, which is of Oligocene age, includes a thin flow of basalt. Flow breccias and minor flows are found in the Oligocene(?) Bas Obispo formation and Las Cascadas agglomerate. Coarse-grained fragmental volcanic rocks, in the form of agglomerates, make up the bulk of the Bas Obispo formation and Las Cascadas agglomerate and occur in other formations of Oligocene and early Miocene age, particularly the Caimito formation of the Gatun Lake area (Oligocene), the Oligocene part of the Caimito formation of Madden basin, and the Panama' formation (early Miocene). Altered tuff is the chief constituent of the early Miocene Cucaracha formation, which underlies the Panama' formation. The Gatuncillo formation (middle and late Eocene) and Chagres sandstone (early Pliocene) contain very little tuffaceous material, and tuff in the middle Miocene Ga tun formation is very fine-grained.
The distribution outlined in the preceding paragraph indicates that the well-dated Tertiary volcanic rocks, including the fragmental volcaiics derived from a nearby source, are of Oligocene and early Miocene age. The volcanic centers presumably were in the area of undifferentiated volcanic rocks in the southwestern part of the area covered by plate 1 or farther west. Maiy remnants of basaltic flows in the southeastern part of the Canal Zone which are not dated, except insofar as they lie on rocks of Oligocene or early Miocene age, probably are of the same age as the better dated volcanic rocks. The fine-grained tuffaceous material in formations of earlier and younger age than Oligocene and early Miocene evidently was erupted at distant localities, probably west of the map area, where a thick


1.4.2.4, lassenose; (4) 11.5.3.5, beerbachose; (5) 111.5.3.4, campsuccession of volcanic rocks is known to be present. The thick succession of that area doubtless includes flows and intrusives younger than those of the map area.
The intrusive Tertiary rocks are intruded into form ations ranging in age from middle and late Eocene to early Miocene. In the Gatun Lake area the Oligocene Caimito formation is intruded by basalt, but no intrusive rocks have been found in the next younger formation-the middle Miocene Gatun formation-or in the still younger Chagres sandstone. In the Gaillard Cut area and still farther southeast, the formations of early Miocene age (Culebra, Cucaracha, and Panama formations) are widely intruded by dikes, sills, and stocks. In that area, however, no Tertiary deposits younger than those just mentioned are recognized and they represent the early half of the early Miocene. If the upper limit of intrusive activity in the Gatun Lake area is applicable in the Gaillard Cut area and farther southeast, none of the intrusive rocks is younger than early Miocene. Some of them, however, may be older. The intrusive rocks, like the volcanic rocks, probably represent the period of time from Oligocene to early Miocene.
The youngest intrusive rocks include the basalt forming dikes that extend around small hills of agglomerate in the Gaillard Cut area (Thompson, 1947a, p. 27; 1952). The agglomerate, which represents part of the Pedro Miguel agglomerate member of the Panami formation, is faulted into the underlying Cucaracha formation along a more or less circular minor fault dipping steeply toward the agglomerate. Movement along the fault may have resulted principally from plastic deformation of the bentonitic clay of the Cucaracha formation. The basalt dike is intruded


56


V


2


22 00 01 01


22. 10.
49. 9.


74 56 25
45


4


2. 40 2. 78 35. 63 21. 68

11. 19 14. 63


3. 06 2. 78 24. 10


5



8. 34 20. 96 24. 74

26. 26 3. 09 4. 75 6. 50 1.82 .93


6


20. 16 7. 78 42. 97 14. 18

.99 1. 63

3. 02 1.22


3. 15

2. 32 .91 1.57


4.
3.
1.


87 19
24


33.


11. 17.

4.
2.


0O

12 40,

17
43 62


_____--._--_ ...







GEOLOGY


along the fault. Drilling through the agglomerate, however, shows that some of the dikes are cup-shaped rather than ring-shaped (Thompson, 1952).

STRUCTURE
STRUCTURAL HISTORY
Late Cretaceous or early Tertiary deforiation.--The
strongest deformation in the known geologic history of the Canal Zone and adjoining parts of PanamS took place after eruption of the Cretaceous(?) lavas and deposition of the interbedded sedimentary rocks and before the laying down of the basal part of the Gatuncillo formation in middle Eocene time. At the present time this deformation is poorly dated and the structural pattern it produced will not be known until the basement rocks are studied and mapped. Almost vertical altered tuffs on the Transisthmian Highway between Rio Gatun and Rio Agua Sucia strike northward. The basement rocks elsewhere in the eastern part of the Canal Zone and nearby show a north-south grain (Jones, 1950, pl. 2). The intrusion of the dioritic and dacitic rocks that metamorphosed the lavas and tuffs probably accompanied the deformation.
Movements during late Eocene(?) to early Miocene
time.-Minor and local movements during middle Tertiary time are indicated by coarse detritus and overlaps. The earliest of these movements, late Eocene or early Oligocene, is suggested by the coarse detritus of the Bohio formation and the overlap of the Bohio on the basement complex in the Pacific coastal area east of the Canal Zone. The source of the coarse detritus may have been beyond the limits of the region covered by plate 1, both to the southwest and northeast.
Minor movement during the middle or late Oligocene is indicated by overlap of the Caimito formation on the Gatuncillo formation in the northern part of Madden basin and by the presumed overlap of the Caimito on the basement northeast of Gatun Lake. Overlap of the Culebra formation on the Las Cascadas agglomerate points to late Oligocene movement.
The overlap of the La Boca marine member of the Panama formation on the Bas Obispo formation suggests comparable minor movement during early Miocene time.
Miocene or Pliocene deformation.-Regional deformation, the second period of regional deformation now recognized, took place during Miocene or Pliocene time. The present structural features of the central Panama area were then formed. The dating is uncertain not only because basic data are still incomplete, but also because the Gatun formation and the Ciagres sandstone do not have an extensive distribution. The Gatun formation, which is of middle Miocene age in the region covered by plate 1, is not known to overlie early


57


Miocene deposits at outcrop localities anywhere in the central Panam area. The structural relations between the Gatun formation and the Caimito forcmation-the next older formation in the Gatun Lake and Caribbean coastal areas-are at present uncknown. The overlap of the Gatun on the basement, however, indicates at least minor movement presumably at the end of early Miocene time and the regional deformation probably took place at that time. The Gatun formation and also the early Pliocene Ciagres sandstone dip gently seaward in the relatively narrow coastal strip where those formations are preserved. The distribution of the Caimito formation and the marine member of the Bohio(?) formation in the western part of the Gatun Lake area indicates a pronounced unconformity between the Gatun and those older formations or that the Gatun is separated from them by a fault. A fault is suggested on plate 1. Minor movement, evidently of late Miocene age, is indicated by the partial overlap of the Chagres sandstone on the Gatun formation. The regional deformation may have taken place in middle or late Pliocene time after deposition of the Chagres sandstorle, but that appears to be unlikely.
How far southward the Chagres sandstone and Gatun formation extended is not known. The Ciagres sandstolce, however, apparently did not extend far. The Toro limestone member, at the base of the Chagres in the northeastern part of its outcrop area, and the Anomia-bearing strata at the base farther southwest are shallow-water deposits. The conglomerate and other deposits at the base of the Gatuns formation between Sabanitas and Maria Chiquita also represent a shallow-water faces. That area, however, is at the east end of the basin. To the southwest, in the Gatun Lake area, the Gatun may have extended considerably beyond its present inland border. The base of the formation east of Zorra Island, however, has not yet been examined and farther southwest the inland border of the formation is under Gatun Lake, and was concealed by extensive swamps before the flooding of the lake. In the area where the inland border of the Gatun is concealed, the middle part of the formation may overlap the lower part, just as farther west, in the region covered by figure 3, the upper part seems to overlap both lower and middle parts. If the formation extended far beyond its present inland border, the submerged area probably passed through Madden basin. Fossils characteristic of the Gatun formation are supposed to have been dredged in Panami Bay off La Boca during the construction of the canal (Li, 1930). Pilsbry, (1931, p. 427-428), who examined the types and figured specimens described by Li, found that the few Miocene fossils, among the Recent species actually dredged i Panama' Bay, are indeed characteristic of the Gatun.







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


One of them, however, is labeled "Gatun Locks and Spillway" and all have a matrix typical of the Gatun formation at and near Gatun. The record of Gatun fossils in Panama Bay is spurious.
STRUCTURAL FEATURES
During the period when geological work was practically limited to a narrow strip along the canal, the canal appeared to cross a major antielinal crest which is located immediately southeast of Gamboa, about halfway across the isthmus, and is essentially parallel to the trend of the isthmus. When two sets of volcanic rocks (Cretaceous(?) and Oligocene to early Miocene) were differentiated, however, it was evident that the anticlinal crest along the canal is a minor feature in a belt of Tertiary rocks extending obliquely across the isthmus.
Plate 1 shows a marked contrast between the Gaillard Cut area and the region to the north and east. Though the numerous minor faults and folds of the Gaillard Cut area reflect the detailed work that has been carried out there, its location with reference to the trough of the Tertiary marine basin may have a bearing on its structural features. The Gaillard Cut area is in the transition zone between a volcanic sequence and a marine sequence, and the cover of sedimentary strata in the transition zone is thin.
The largest well-defined folds-Madden basin and Quebrancha syncline-lie east of the Canal Zone in the trough of the Tertiary marine basin. Madden basin has the greater structural relief. It is the only area where late early Miocene marine deposits have been found and they are almost exactly at the middle of the isthmus. Madden basin is a broad gentle fold trending north-northeastward. Toward the south it flares out in an area where the geology is not well known. As shown by Reeves and Ross (1930, pl. 6), a narrow belt of relatively steeply dipping rocks (20' to 450) extends northward from Rio Chagres on the west side of the basin. The floor of the basin may be irregular through overlap of the Bohio formation by the Caimito formation.
Quebrancha syncline also trends north-northeastward, but is more sharply folded than Madden basin. The southward-plunging anticline between Quebrancha syncline and Madden basin is greatly modified by the Lim6n fault.
The northeastward trending anticline in Bohio Peninsula, in the Canal Zone, appears to be well defined. The interpretation that it extends farther southwestward, and there reaches its greatest structural relief, is adopted to account for the upper Eocene or lower Oligocene strata of the marine member of the Bohio (?) formation in the northern part of the peninsula ending in Palenquilla Point and on Trinidad Island.


Evidence for a major eastward-trending fault, just north of Trinidad Island and just south of the Brujas Islands, is presented on page 61. So far as known the faults are steeply dipping normal faults and many of them probably have strike-slip displacement (Jones, 1950, p. 906). Most of the major faults have a general northward trend, but the trend of that group of faults ranges from about N. 300 W. to about N. 30' E. A few major faults, such as the Rio Gatd'n fault and a fault along the lower course of Rio Frijol northwest of Gamboa, trend more to the east, about N. 70' E. The Chinilla fault, one of the group of major faults having a general northward trend, lies close to the Panama Railroad south of the embayment of Gatun Lake formed by Rio Agua Salud and Rio Frijolito. When MacDonald and Vaughan examined the fresh cuts and collected fossils from the Caimito formation along the railroad in 1911, they had no way of knowing that strata older than any along the canal or railroad (strata of the Gatuncillo formation) crop out only 200 meters east of the railroad.
Jones' geologic map of the Gatun Lake area (1950, pl. 2) shows many faults and fractures not shown on plate 1 of the present report.
The structure of the volcanic rocks west of Gaillard Cut is practically unknown. Detailed field work east of the Gaillard Cut area should show whether there is any correlation between the thin sedimentary cover and the structure of the Gaillard Cut area. Two characteristic formations of the thin sedimentary cover do not extend far east; the Culebra and Cucaracha formations. The distribution of those two formations in the complexly faulted Gaillard Cut area determined the course of the canal. Both are readily eroded and form topographic basins between irregularly arranged hills of basalt and agglomerate.

MINERAL RESOURCES
METALLIC MINERAL DEPOSITS
Gold.-Gold ore has been mined in two districts: in the basement rocks southeast of Sabanita and at a stock of dacite porphyry southeast of Gamboa.
I am indebted to R. H. Stewart for guiding me to the area southeast of Sabanita. Evidence of three periods of mining activity may be seen along streams immediately north and northeast of Cerro Santa Rita (at the summit of which is located the 268-meter triangulation station plotted on plate 1): remnants of large stone mortars pointing to aboriginal operations; caved and also almost imperceptible adits associated with a French boiler still standing upright; and modern adits. The aboriginal operations suggest the origin of the name for Bahia de las Minas, the bay into which the streams drain. When Mr. Stewart first visited this


58







GEOLOGY


region in 1947, the boiler fire-box door (now missing) bore the name of a French manufacturer and the date 1883. The country rock is olivine-rich basalt, a typical exposure of which is readily accessible at the Transisthmian Highway bridge across Quebrada L6pez, a small stream 1% kilometers in a direct line northwest of the junction with the road to Nueva Providencia. The ore occurs in sulphide-bearing small quartz veins. No data are available on the mineralogy and tenor of the ore or on the tonnage that has been mined.
Gold-mining operations at a stock of dacite porphyry southeast of Gamboa were carried on near the head of Quebrada de Oro, a small northwestward-flowing tributary of Rio Casaya. Locality 38 is located on Quebrada de Oro downstream from the adits (pl. 1). Remnants of mine and mill machinery and stretches of tram track are strewn along the stream. Mr. Adrian Bouche, of Pedro Miguel, the present owner of the property, orally reported that an English Company installed the mine and mill in the late 1870's or early 1880's, but that there is no evidence any gold was produced. The adits are located in a narrow aureole of mildly contactmetamorphosed sedimentary rocks of the Gatuncillo formation at the border of the porphyry stock. No attempt was made to enter the caved adits.
Other adits and pits are located in the same stock of dacite porphyry, across the divide and 700 meters south of locality 38, near the head of a tributary of Rio Sardanilla, which flows southward and westward toward the Panama Canal. Boutan (1880, p. 31-32) mentioned a road built to haul machinery to a gold mine on Rio Sardanilla. The last French map, in the report of a Commission of the second French canal company that includes an account of the geology by Bertrand and Znrcher (1899), shows near Rio Sardanilla a "mine de quartz aurifere en exploitation."
In his unpublished manuscript, written about 1918 and mentioned on page 4 of the introduction of the present report, MacDonald reported that none of some 40 samples from the most promising veinlets, "about 2% miles east of the canal opposite Las Cascadas," showed gold values of more than $1.00 to the tol. That statement evidently refers to the Quebrada de Oro area. He also reported on samples collected "a mile more or less in a southeasterly direction from these [those of preceding two sentences] old workings"; that is, in the Rio Sardanilla area. The gold value of his samples is as follows:


59


Gold value (as of about 1912) of samples collected in Rio Sardanilla
area
[Extracted from manuscript by D lacDonaldj
Value of gold
Sample per too Float from quartz vein-- - $6. 80 End of open cut__.---__-_-_---------------------- 1. 04
Open cout ----------- 41
Outerop, 'op of ridge -------- .20 Lower Cart of cot- -------T race
Manganese.-Plate 1 was extended far enough to the north to show the location of the southern of two manganese prospects near Rio Boquerdn. An abandoned tram line extends from the prospects to the coast near Nombre de Di6s. The country rock consists of strongly deformed, low-grade metamorphic rocks-quartzite, siliceous limestone, micaceous seloist (probably metamorphosed tuff), and greenstone (highly altered alglomerate)-all representing the Cretaceous(?) basement complex. The ore deposits are manganese oxides associated with red jasper. Boulder-like masses of ore form great trains down the slopes and streams. These deposits were described briefly by Sears (1919) and are described in greater detail by Simons in a recent publication (Roberts, R. J., and Irving, E. M., 1917, p. 119128), fromwhich the preceding sentences were abstracted.
In the publication just cited Simons mentions a minor manganese prospect in Madden basin, south of Rio Chilibrillo and about 2 kilometers south of Casa Larga. According to a written communication from T. F. Thompson, shallow pits and trenches scattered over an area of about a hectare show aggregations of manganiferous concretions and lenses in the Bohio formation.
NONMETALLIC MINERAL DEPOSITS
Limestone for cement.-Limestone in the Quebrancha limestone member of the Coimito formation is at present the most important nonmetallic mineral deposit. The limestone is quarried by the Cia. Cement Panama', S.A., immediately east of the Transisthmian Highway on the east limb of the Quebrancha syncline (locality 62, pl. 1) and is processed as an ingredient for cement in the company's adjoining plant. The thickness and properties of three grades of limestone and one of calcareous siltstone are described in Thompson's (1944) detailed report. The reserves are enormous.
Other limestones in the Caimito formation of Madden basin and the Gatun Lake area, the Emperadorlimestone member of the Culebra formation, and at the base of the La Boca marine member of the Panamd formation







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


may be suitable for cement. According to an oral communication from Thompson, the widespread limestones of the Gatuncillo formation are too high in magnesia.
Rock for construction.-MacDonald (1915, p. 35-38) adequately covered construction material used in the building of the canal. The great quarry in dacite on the west face of Ancon Hill, the quarry in basalt at Sosa Hill adjoining the Balboa docks, and the quarry in basalt on the west side of the Panama Railroad 3 kilometers northwest of Monte Lirio, are reminders of the construction period.
Since MacDonald wrote his account, a quarry has been opened in hornblende andesite on the Chiva Chiva Road 6% kilometers northeast of Pedro Miguel.
OIL POSSIBILITIES
Though the central Panami. area of Tertiary marine sedimentary formations is small and the total thickness of marine strata is moderate, the oil possibilities deserve consideration, especially since the discovery in 1956 of oil in the Costa Rican part of the Bocas del Toro area. The southeastern end of the Costa Rican part of the Bocas del Toro area is shown in figure 1. At the time of writing (Sept., 1956) the discovery well, Union Oil Co. No. 2 Cocoles, located 1% kilometers north of the international boundary, had just been completed and stratigraphic data had not been released.
In many respects the stratigraphic succession in the southeastern part of the Bocas del Toro area is similar to that in the central Panamd area, which includes the Canal Zone. On the islands of Bocas del Toro Archipelago a thin section of carbonate and other rocks of Pliocene age crops out. They are underlain in the archipelago and on the mainland by Miocene strata, designated by Olsson the Gatun stage or formation (Olsson, 1922, p. 10-16). The upper part of Olsson's Gatun consists of carbonate and fine-grained, calcareous detrital rocks of late Miocene age, correlated with the upper part of the Gatun formation in the western area of the present report. The lower part of Olsson's Gatun corresponds to the late middle Miocene middle part of the Gatun in the Canal Zone and also to the late middle Miocene upper part in the eastern area, although the depth-facies in the Bocas del Toro basin is shallower than that of the upper part in the Canal Zone. The equivalent of the early middle Miocene lower part of the Gatun in the Canal Zone is missing at the outcrop in the Bocas del Toro area or is partly represented by nonmarine conglomerate, rocks of finer


grain containing land plants, and lignite. Olsson's Gatun rests unconformably on the Uscari formation (or better Uscari shale), which consists almost entirely of moderately deep-water fine-grained rocks (Olsson, 1922, p. 10). Light oil issues from fractures in strongly deformed strata of the Uscari in the type region along Uscari Creek. The Uscari is of late Oligocene and early, Miocene age and corresponds in age to the Caimito formation of Madden basin. The oldest outcropping Tertiary strata in the southeastern part of the Bocas del Toro area are limestones, probably of both Oligocene' and Eocene age. The presence of subsurface marine strata of Eocene age is a reasonable expectation. There are two important differences between the two areas. No oil seeps have been found in the central Panama area and nothing in the Oligocene and lower Miocene outcrop section closely resembles the almost uniformly fine-grained rocks of the Uscari shale.
Three districts in the part of the central PanamiA area covered by plate 1 are promising for testing oil possibilities: the Gatun Lake district, Madden basin, and the Pacific coastal district east of Panama City.
Gatun Lake district.-Estimates of outcrop and probable maximum subsurface thickness in the Gatun Lake district are as follows.

Estimated outcrop and probable maximum subsurface thickness of
sedimentary rock formations in Gatun Lake district


Formation
Chagres sandstone Deposits of late Miocene age Gatun formation Deposits of early Miocene age Caimito formation Bohio formation--- - -- - Marine member of Bohio(?) formation
Gatuncillo formation

Total


subsurface outcrop thickness thickness in
in meters meters
250 250 Overlapped 100 250 500 Overlapped 300 300 400 300 300

100 250 25+ 300

1, 225+ 2, 400


The outcropping formations in the Gatun Lake district are marine, with the exception of the Bohio formation, which is nonmarine throughout most of the area. On Barro Colorado Island, however, the upper part of the Bohio includes thin marine tongues of somewhat calcareous, medium-grained subgraywacke, suggesting that the nonmarine coarse-grained rocks are replaced seaward by marine rocks of finer grain.
The upper part of the Gatun formation consists of more or less calcareous, sandy and silty rocks containing


60


I






GEO

i clay-like matrix. The fauna, which includes pelagic Foraminifera, a few pteropods, and a rich assortment of benthonic foraminifera and mollusks, indicates a moderate-depth environment (50 to 100 fathoms; outer neritic zone of forthcoming "Treatise on paleoecology" to be published by the Geological Society of America). The late Miocene upper part of the Gatun in the western area, west of the Canal Zone (fig. 3), is overlapped by the Cliares sandstone, but is presumed to be present in the subsurface section.
Deposits of early Miocene age are unknown in the ,Gatun Lake district. That they were deposited there is indicated by the Caribbean faunal affinities of the early Miocene part of the Caimito formation in Madden basin. As it is unlikely that they were removed before deposition of the Gatun formation, it is concluded that they are overlapped by the Gatun, which, along the northeast border of the central Panamni area, overlaps the Caimito formation and rests on the Cretaceous(?) basement.
Except on Barro Colorado Island, the Caimito foriiation consists of moderately coarse, shallow-water, highly tuffaceous rocks and thin algal-foraminiferal limestone. Though the lower part of the Caiito on Barro Colorado includes thun algal-foraminiferal limestone, it is made up chiefly of medium- to very finegrained, somewhat tuffaceous sandstone. These finegrained rocks contain a moderate-depth fauna. At one locality (54n) silty, very fine-grained sandstone contains numerous discoasters and other pelagic coccolithoplhores and numerous pelagic Foraminifera. The outcrop section of the Caimito on Barro Colorado, like that of the Boleo formation, points to progressively deeper water and finer grain size in a seaward direction.
By the same line of reasoning outlined for deposits of early Miocene age, the Gatuncillo formation is expectable in the subsurface section of the Gatun Lake district. That expectation recently was realized, when the Gatuncillo was indentified at a depth much shallower than expected. In 1955 R. H. Stewart, of the Panama Canal Company's Meteorological and Hydrographic Branch, examined the cores obtained in Core Hole CH-5, drilled in 1946 at a locality in Gatun Lake 325 meters south of Guava Island, a small island of the Brujas Islands group. (The core-hole locality is 1.3 kilometers east of locality 55a of plate 1.) The cores include a considerable thickness of fossiliferous limestone, logged as part the Caimito(?) formation when the core hole was drilled. Mr. Stewart, however, thought it probably is a limestone of the Gatuncillo formation and his suspicion was confirmed when W. S. Cole identified Heterostegina ocalana, Lepidocyclina macdonaldi, L. chaperi, and Asterocyclina georgiana in
413788-57-5


LOGY


61


a sample of readily disintegrated limestone from the core. A synopsis of the core is as follows:
Log of Core H1ole CH--5, drilled in Gatun Lake
Thikess
Lake sediments --_-----_-----_------------5 9
Caimito(?) formation:
eetotnitic tuff grading downward into sandy siltstone
is beset 3 in----------------------ii1.2
Gatuncilio formation:
Hard fossiliferous limestone grading downwvard into
soft mariy lieestone in lower 1.9 i s ---- 5
Sandv siltstone and thin beds of tuff and limestone-.. 14. 4


Total thickne,


38. 0


The presence of the Gatuncillo formation 11.2 meters below the bottom of the lake sediments can hardly be accounted for without in assumption of a major fault trending a little north of east and lving just north of Trinidad Island and just south of the Brujas Islands group. The Caimito formation is not kisonii to overlap the Bohio formation anywhiere in the central part of the Gatun Lake area, although in the northeastern part of the area, north of Nueva Providencia, it evidently overlaps both Bohio and Gatuncillo. The strata in the core hole overlying the Gatuncillo formation do not suggest overlapping deposits. Nevertheless the siltstone strongly suggests the tuffaceous siltstone of the Caimito exposed on the south coast of Pato Horqueto Island (locality 55a, pl. 1), the island in the Brujas group west of the core-hole site. If these suggestions are correct, the core hole passed through a fault at a depth of 29.7 meters below the surface of the lake-a fault having a stratigraphic displacement of about 300 meters. No evidence indicating a fault, however, was recorded by the geologist who prepared the log. As a matter of fact, a fault of that character and of the trend just specified accounts for the marine member of the Boheio(?) formation on Trinidad Island much more satisfactorily than plate 1. The Gatuncillo formation, consisting chiefly of ioderate-depth siltstone and mudstone, is a likely source for oil throughout the central Panama. area and its limestones are suitable reservoirs.
Madden basin.-The following table shows estimates of outcrop and probable maximum subsurface thickness in Madden basin.
Estimated outcrop and probable maximum subsurface thickness of
sedimentary rock formations in Madden basin
Maximum
Outcrop subsurface
thickness thickness
Formation (meters) (7neters)
Caet eite ------------- ---- 459 459
Bebie foratio-------------- 0-290 399
Gatuncilo formation------ -- 300 500
Total ..---- ..---- .------- 750-950 1. 250







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


As in the Gatun Lake district, the bulk of the Bohio formation consists of nonmarine boulder conglomerate. At the continental divide the upper part of the formation includes thin lenses of algal-foraminiferal limestone. In the Quebrancha syncline, northwest of Madden basin, the Bohio is made up of graywacke grit, the basal part of which includes marine siltstone. In the northern part of Madden basin the Caimito formation overlaps the Bohio.
The Gatuncillo formation evidently rests on an uneven surface of the basement complex. Reeves and Ross (1930, p. 18, pl. 5) mentioned and mapped a small outcrop of dioritic rock near the head of Rio Azote Caballo, just south of the present south shore of Madden Lake. This outcrop evidently is the top of a basement hill or ridge, on the sides of which the Gatuncillo is overlapped by the Caimito. Practically pure quartz sandstone in the upper part of the Gatuncillo is exposed along the road from Casa Larga to Laguna, near locality 13-the only locality where such sandstone was observed in the area covered by plate 1.
Pacific coastal district east of Panamd City.-In the Pacific coastal district east of Panama' City, the Gatuncillo formation is overlapped by the Bohio formation. The Gatuncillo reappears farther east in the valley of Rio Bayano, 45 kilometers east-northeast of the eastern border of plate 1 (Terry, 1956, p. 32).

DESCRIPTION OF TERTIARY MOLLUSKS
The formal description of species is held to a minimum. Lengthy descriptions almost invariably include matter at the generic level which is of no value in the discrimination of species.
The following terms are used for type material of species:
Type: A specimen selected by the describer as the namebearer of a species. Also known as holotype.
Paratype: A specimen showing a feature, or features, not
shown by type. Also used by others for any specimen, other than type, on which the description of a species is
based.
Syntype: A specimen in a lot of two or more on which a
species is based, but none of which was selected by the
describer as the name-bearer. Also known as cotype.
Lectotype: A syntype subsequently selected as the namebearer.
Neotype: A specimen, from the same locality and horizon,
selected as the name-bearer to take the place of destroyed
or lost type material.
Topotype: A specimen from the same locality and horizon
as the name-bearer.
Terms used for types of genera are as follows:
Orthotype: Type by original designation.
Monotype: Type by monotypy. Also known as haplotype.
Tautotype: Type by tautonymy.
Logotype: Type by subsequent designation.


Adoption of the preceding terms for the types of J genera, which have the advantage of brevity, was prompted by Iredale's (1939, p. 223) usage in his Greatt Barrier Reef report. Monotype, however, has beei substituted for haplotype. Iredale's usage was base{ on Jordan's, who in turn picked up terms from Cooke,k but also added one of his own. Those interested in thy origin and varying usage of the terms in the preceding: two lists will find definitions and citations in Frizzell's useful "Terminology of types" (1933). It is entirely appropriate to use the term "type" for a species and a genus. There can be no confusion: the type of a species is a specimen, whereas the type of a genus is a species.
The following new subgeneric names are proposed:
Aepystoma, subgenus of Teinostoma, Vitrinellidae.
Type: Teinostoma (Aepystoma) andrium Woodring, n.
sp., Gatun formation, Miocene, p. 70. Gender neuter."
Diaerecallus, subgenus of Teinostoma, Vitrinellidae.
Type: Teinostoma (Diaerecaluns) .sychnum Woodring, ni.
sp., Gatun formation, Miocene, p. 71. Gender mascul
line.
Hapalorbis, subgenus of Solariorbis, Vitrinellidae.
Type: Circudus liriope Bartsch, Recent, Gulf of California, p. 75. Gender masculine.
Hypterita, subgenus of Neverita, Naticidae, Polinicinae.
Type: Natica helicoides Gray, Recent, Baja California
to Perd, p. 92. Gender feminine.


GASTROPODS


I


Family TROCHIDAE
Trochids are rare in the Tertiary formations of the Canal Zone and adjoining parts of Panama. Each of the two species of Calliostoma herewith described is represented by two specimens. In addition three othet trochids are recognized: a minute "Margarites" from the middle part of the Gatun formation; an exfoliated apical fragment sculptured with nodose spirals, evidently a calliostome, also found in the middle part of the Gatun formation; and an incomplete impression, probably a calliostome sculptured with weakly noded spirals, from the Toro limestone member of the Chagres sandstone. Each of these three trochids is represented by only one specimen.

Subfamily MARGARITINAE
Genus?
"Margarites" species
Minute, very thin-shelled, outline naticid, whorls rapidly enlarging. Protoconch consisting of a smooth naticoid whorl. End of protoconch marked by fine closely spaced axial and spiral threads. Both sets of threads gradually become more widely spaced and on later part of penult they disappear, the early part of the penult bearing a sutural thread, a thread on the shoulder, and widely spaced retractive axial threads


62






GASTROPODS: TROCHIDAE TO TURRITELLIDAE


between them. Body whorl smooth. Outer lip broken ar back. Columellar lip incomplete. Umbilicus evilently very narrow, umbilical border broadly rounded. Height 2.4 mm, diameter 2.2 mm.
This curiously sculptured species represents ain un'nown genus of the Margaritinae. The outline and thin shell suggest "Solariella" iridea Dall (1889, p. 382), IJredged by the Blake off Cape Florida at a depth of
_193 fathoms. "Solariella" iridea, however, has more inflated whorls, no axial sculpture, a faintly undulated spiral near the suture, a wider umblicus, and elongate nodes on the umbilical border. Though "Solariella" iridea was described as a variety of "Solariella" lubrica Dall, it is not closely related to that species, which is the type of the genus Suavotrochus (Dall, 1924, p. 90), described as a section of Solariella.
Occurrence: Middle part of Gatun formation (middle Miocene), eastern area, locality 155c.
Subfamily CALLIOSTOMATINAE
Genus Calliostoma Swainson
Swajesen, A treatise en mnalaelegy, p. 351, 1840. Type (logotype, Herrmanesen, Indicis generum malacozoorum,
v. 1, p. 154, 1846): Trochus conulus Linn6 (cited by Swainson
as "conula Mart."), Recent, Mediterranean Sea.
Subgenus Calliostoma s. s.
Calliostoma (Calliostoma) metalium Woodring, n. sp.
Plate 18, figures 12-14
An imperforate very weakly sculptured, nonnoded, carinate callistome of medium size. Whorls rapidly enlarging, outline of spire concave. Whorls, except body whorl of mature shells near outer lip, very strongly carinated by a peripheral spiral, which is visible on spire whorls adjoining anterior suture. Three weak spirals visible on earliest preserved whorl, which is somewhat exfoliated. A few very faint spirals visible on anterior part of other spire whorls. Body whorl between suture and periphery bearing weak spirals. Base bearing faint spirals adjoining periphery and wider faint spirals adjoining columellar lip. Columellar lip everted, molded against base of shell except nar base of lip.
Height (almost complete, but crushed) 19.5 mm, diameter (incomplete) 24 mm (type).
Type: USNM 561430.
Type locality: 206a (Stanford Univ. locality 2699, Caribbean coast near mouth of Rio Pina, road cut on west side of river about 90 n. west of road fork, Panamd; same locality as USGS 16937), Chagres sandstone.
Though the type is somewhat crushed and evidently is immature, the characters of this weakly sculptured, nonnoded, carinate species are well defined. Much of the type is more or less exfoliated, but even unex-


foliated patches are very weakly sculptured, aside from the strong peripheral spiral. That the type is not mature and that the peripheral spiral is reduced near the outer lip of mature shells are shown by an exfoliated body whorl fragment from the type locality-the only specimen other than that illustrated. This fragment indicates a body-whorl diameter of at least 30 millimeters.
In outline of spire, strongly carinate periphery, and almost smooth base, Calliostoma metalium is allied to C. aurora Dall (1889, p. 366, pl. 37, fig. 2), dredged at a depth of 140 fathoms off Barbados. (Dall also recorded a fragment from a depth of 576 fathoms.) C. metalium, however, lacks the noded spirals of C. aurora and the basal spirals of the fossil are even weaker.
Occurrence: Chagres sandstone (early Pliocene), localities 206, 206a.
Subgenus leiotrochus Conrad
Conrad, Acad. Nat. Sci. Philadelphia Proc., p. 288, 1862. Type (monotype): Leiotrochus distant Conrad, Miocene,
Maryland.
Assignment of Calliostoma eremum to Leiotrochus has the advantage of indicating that this species has an umbilicus. It is doubtful, however, whether the strongly sculptured C. eremum and its allies are closely related to the faintly sculptured C. distans. For the characters of C. distans, reliance is placed on specimens in the U. S. National Museum from Yorktown, Virginia, labelled C. briani Conrad. According to Dall (18901903, pt. 2, p. 402, 1892), who handled specimens identified by Conrad, C. briani is C. distans. The C. distans of the Maryland Geological Survey Miocene volume (Martin, 1904, p. 258, pl. 61, fig. 6) is imperforate and has moderately strong sculpture. Evidently it is not C. distans, as it does not agree with Conrad's description.
As suggested by Gardner (1926-47, p. 619-620, 1947), a more natural grouping of perforate and imperforate species of Calliostoma may possibly be gained through a study of the development of the sculpture.
Calliostoma (Leiotrochus) eremum Woodring, n. sp.
Plate 22, figures 3,5
A perforate calliostome of medium size. Whorls of spire slightly inflated, body whorl strongly inflated. Sculpture of spire whorls and of body whorl between periphery and suture consisting of strongly noded. primary spirals (3 on earliest preserved whorl, 5 to 6 on penult, and 9 to 12 on body whorl). A weakly noded secondary spiral in some interspaces. On late whorls some secondary spirals are transformed into primaries by becoming wider and more strongly noded. Base sculptured with 10 or 11 primary spirals. A


63







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


secondary spiral present or absent in interspaces on base. Nodes on basal spirals long, low, and not well defined. Edge of umbilicus not sharply angulated and therefore junction of basal and columellar lips not angulated. Interspaces on base and umbilical wall adjoining innermost basal spiral roughened by axial wrinkles. Remainder of umbilical wall smooth, aside from subdued growth lines.
Height (incomplete) 17.5 mm, diameter 19 mm (type). Height (almost complete) 18.7 mm, diameter 19 mm (paratype).
Type: USNM 561311; paratype, Stanford Univ.
Type locality: 155c (USGS 16915, Gatun Third Locks excavation, east side of excavation, 1 mile (1.6 km) north of Gatun Lake, Canal Zone), middle part of Gatun formation.
This species is represented by two specimens, both collected at the Gatun Third Locks. It has a less angulated umbilical border than Calliostoma grabaui Maury (1917, p. 155, pl. 24, fig. 19), from the middle Miocene Gurabo formation of the Dominican Republic, and also has weaker nodes on the spirals of the body whorl, particularly on the base. C. mancinella Olsson (1922, p. 164, pl. 15, figs. 9, 10), from the middle Miocene of Costa Rica, has a lower spire, less inflated spire whorls, and more widely spaced basal nodes. The more inflated spire whorls and less angulated umbilical border of C. eremum differentiate it from the living 0. sayanum Dall (1889, p. 370, pl. 33, figs. 10, 11), which furthermore is twice as large. The two specimens of C. sayanum mentioned by Dall in 1889 still are the only representatives of that species in the collections of the U. S. National Museum: the type dredged at a depth of 120 fathoms 20 miles southeast of Cape Hatteras and a body-whorl fragment from a depth of 107 fathoms 36 miles south of Cape Hatteras.
Occurrence: Middle part of Gatun formation (middle Miocene), eastern area, localities 155, 155c.
Family TURBINIDAE
Genus Turbo Linn6
Linn6, Systema naturae, ed. 10, p. 761, 1758. Type (logotype, Montfort, Conchologie syst6matique, v. 2,
p. 203, 1810): Turbo petholatus (Turbo petholatus Linn6),
Recent, tropical western Pacific and Indian Oceans.
Subgenus Marmarostoma Swainson
Swainson, Zoological illustrations, 2d ser., v. 1, text accompanying pl. 14 (unnumbered), 1829.
Type (orthotype): Turbo chrysostomus Linn6, Recent, tropical
western Pacific.
When Swainson proposed the generic name Marmarostoma, he designated Turbo chrysostomus as the type. The only species of Marmarostoma, however, described by him at that time, M. undulata (correctly M. un-


dulatum), evidently is the Panamic species named, Turbo saxosus by Wood (1828, p. 20, pl. 6, fig. 45) a year earlier; that is, it is a species of the subgenus Callopoma Gray (Gray, M. E., 1850, p. 87; type (logotype, Cossmann, 1895-1924, pt. 11, p. 116, 1918):11 Turbo fluctuosus Wood, cited by Cossmann as Turbo fluctuatus Gray), Recent, tropical eastern Pacific),t characterized by a deep central pit and granular ribs on the operculum.
Many years ago Iredale (1915, p. 444) discussed Swainson's type designation, but, apparently on th tacit assumption that Turbo marmoratus Linn6 is the type of Turbo, he considered Marmarostoma to be a, synonym of Turbo. Thiele in his Handbuch der svstematischen Weichtierkunde and Wenz in his treatise on fossil gastropods have called attention to the availability of Marmarostoma in place of the better known Senectus Swainson (1840, p. 348; type (logotype), Herrmannsen, 1846-52, v. 2, p. 438, 1848: Turbo chrys, ostomus Linn6, (cited by Swainson as "chrysostomus Mart."), which is an objective synonym.
Caribbean fossil and Recent species that are referred to Afarmarostoma are not typical of that subgenus. The operculum of Turbo chrysostomus and its close allies has marginal oblique nairow grooves separating minutely granular bands, whereas the operculum of the Caribbean species has a more or less distinct shallow marginal ledge and is faintly granulai or smooth.
Turbo (Marmarostoma) aff. T. castaneus Gmelin Plate 20, figure 10
Of medium size, sculpture nonlamellar. Early whorls bearing a conspicuous practically smooth basal spiral. Later whorls weakly shouldered, sculptured with noded spirals. Somewhat worn operculum assumed to represent this species is smooth, bearing a poorly defined shallow marginal ledge.
Height (not quite complete) 20.5 mm, diameters (incomplete) 18 mm (figured specimen). An incomplete apparently immature shell and asso-4 ciated operculum from the middle part of the Gatun formation and a mold of a few whorls from the Toro limestone member of the Chagres sandstone are identified as Turbo aff. T. castaneus. They may, in fact, represent the Recent Caribbean T. castanets. The operculum fitted into a shell considerably larger than the only shell collected at the same locality.
The typical form of T. castaneus, as long accepted, is sculptured with nonlamellar noded spirals. Recent Caribbean shells that have noded spirals but also have thin lamellae forming vaulted scales on the primary spiral at the shoulder, or on that spiral and others, have been referred to T. crenulatus, also named by Gmelin. T. crenulatus has the same geographic range


164






GASTROPODS: TROCHID

-I's T. castaneus (North Carolina to the West Indies), cut is said to be more common at slightly shallower leptis (Dall, 1890-1903, pt. 2, p. 382, 1892). It has een considered a synonym of T. castaneus, a variety if castaneus, or a valid species. The collections of the J. S. National Museum indicate that the two forms ntergrade. They are considered forms of a variable species, at least until more is known about their habitat cnd habits.
The fossils from Panama are nonlamellar. They are not as strongly shouldered as most Recent shells-that is, the spiral at the shoulder is not as strong-and the nodes on the sutural spiral, particularly on the specimen lrom the Gatun formation, are not as coarse as those of most Recent shells. In both features, however, a few Recent shells closely approach the fossils.
Other fossils suggest that Turbo castaneus was living in the Miocene Caribbean Sea. A small incomplete strongly shouldered lamellar specimen from the middle Miocene Bowden formation of Jamaica is recorded as Turbo (Senectus) species (Woodring, 1928, p. 411). A strongly shouldered nonlamellar form, Turbo (Senectus) cf. castanes (Rutsch, 1934, p. 40, pl. 1, figs. 1, 2) occurs in the late Miocene Punta Gavilain formation of Venezuela. Turbo crenulatoides Maury (1917, p. 153, pl. 24, fig. 14), from the middle Miocene Cercado and Gurabo formations of the Dominican Republic, is sculptured with strong lamellae that extend from sutcre to base on the body whorl. It is doubtful, however, whether it can be differentiated from strongly lamellar Recent shells.
Late Miocene deposits in western Florida yielded a strongly shouldered Turbo bearing a few lamellae on spirals below the shoulder on the later part of the body whorl. It was recorded as Turbo castaneus var. crenulates (Mansfield, 1930, p. 127, pl. 19, fig. 5). T. castaneus and T. castaneus var. crenulatus are recorded from the Pliocene Caloosalcatchie formation of Florida. I Occurrence: Middle part of Gatun formation (middle Miocene), eastern area, locality 155b. Toro limestone member of Chagres sandstone, (early Pliocene), locality 196.
Family PHASIANELLIDAE
When the family name Tricoliidae was used in 1928 (Woodring, 1928, p. 418), it was not intended as a new name. It was used under the impression that the name had been proposed or suggested: evidently the result of an erroneous interpretation, perhaps of Iredlae's (1924, p. 232) statement. At, all events the name is to be suppressed, for Tricolia appears to be properly referred to the family Phasianellidae.
Genus Tricolia Risso
Risso, Histoire naturelle des principles productions de
lEurope n6ridionale, v. 4, p. 122, 1826.


Type (logotype, Gray, Zool. Soc. London Proc., p. 144, 1847):
Turbo pdlus (Titrbo pullus Linn6), Recent, Mediterranean.
(Gray cited the generic name as Tricolea.)
Before the generic name Tricolia can be used it is necessary to dispose of Lamarck's name Phasianella (1804, p. 295). Though that name appeared in a publication on fossils from the vicinity of Paris and two Eocene species are the only ones that were described, Lamarck stated that he was naming the genus for a Recent shell, "faisan (phasianus)". Despite Lamarck's clear intention and although there is no doubt about the identification of the shell lie mentioned and partly described, he cited no references that could be used in fixing its Latin name. Therefore the view that faisan (=Bucciaum australis Gmelin) is the type by original designation (Woodring, 1928, p. 418, 419, footnote) is hardly admissible. I am indebted to H. A. Relcder for pointing out that the deficiency in Lacmarck's treatment was rectified within the next year by Roissy (1805 or 1806, p. 330), when he wrote "Le type de ce nouveau genre, que l'on doit encore h M1. de Lamarck, est une jolie coquille appelse/faisan, *.' He stated that this species is from New Holland and on the next page described it as Phasianella variegata, citing Buccinum tritonis Chemnitz in synonymy. This is an unequivocal type designation and it is irrelevant that Lamarck used only a vernacular name for the type species. The type of Phasianella therefore is P. variegate Roissy (=BBuccinum australis Gmelin). Roissy's action fortunately saves the traditional usage of Phasianella.
Tricolia calypta Woodring, n. sp.
Plate 15, figures 1, 2
Of medium size, moderately inflated, spire high. Columellar lip and parietal callus thin. Umbilical groove narrow. Type showing curved strongly retraclive bands on later part of body whorl, bands standing out in slight relief on the somewhat altered and corroded shell, but iay originally ihave been color bands. Operculum unknown.
Height 4.8 min, diacieter 3.1 imm (type).
Type: USNM 561327.
Type locality: 40a (USGS 2683, Vamos Vamos, off Palenquilla Point, Canal Zone, now submerged), marine ccember of Bohio(?) formation.
The type and an additional specimen are in one of Hill's collections from Vanos Vamcos, and two others are in McIcDonald and Vaughan's collection from the same locality. The type is the only specihne that shows the retractive bands.
The whorls of Tricolia calypta are less constricted at the suture than those of T. precursor (Dall) (1915, p. 94, pl. 12, fig. 5), and the species from Panami has a


AE TO TURRITELLIDAE


65







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


narrower umbilical groove. T. precursor occurs in the early Miocene Tampa limestone of Florida.
In Europe Tricolia is recognized in strata as old as Paleocene, but T. calypta is the earliest American species so far described.
Occurrence: Marine member of Bohio(?) formation (ate Eocene or early Oligocene), Gatun Lake area, localities 40a, 40d.
Family PHASIANELLIDAE?
Tricolia? syntoma Woodring, n. sp.
Plate 17, figure 47
Small, strongly inflated, spire low, outline like that of a minute naticid. Columellar lip wide, its outer edge bearing a faint low narrow rim. Parietal callus thick, continuous with the columellar lip, its edge sharply defined. Umbilical groove very narrow, almost closed. Operculum unknown.
Height 2.2 mm, diameter 2.2 mm (type).
Type: USNM 561328.
Type locality: 170a (USGS 8411, headwaters of 'Quebrada Cafna (Rio Caflo Quebrado), Panami, middle part of Gatun formation.
The family and generic assignment of this minute species, represented by one specimen from the middle part of the Gatun formation, are doubtful. Some features suggest a low-spired Tricolia, but no species of Tricolia examined has a wide-rimmed columellar lip. The type and only specimen of "Eucosmia" lurida Dall (1897, p. 15, pl. 1, fig. 11) in the collection of the U. S. National Museum (a Recent shell from British Columbia) has a wide distinctly rimmed columellar lip, which is not shown on the poorly drawn aperture of Dall's illustration. This species, however, is probably a Homalopoma related to H1. subobsoletum (Willett) (1937, p. 63, pl. 25). Most species of Tricolia have a thin parietal callus that fades out on the parietal wall. Nevertheless some species have a moderately thick callus that joins the columellar lip. Despite its relatively narrow aperture, Tricolia? syntoma may represent an undescribed turbinid genus remotely related to Homalopoma.
In outline Tricolia? syntoma suggests the Miocene Jamaican species Tricolia (Eulithidium) hadra Woodring (1928, p. 420, pl. 34, figs. 10, 11) and a minute Recent Cuban Tricolia described by Dall (1889, p. 351, pl. 19, fig. 10b) as "Phasianella (Eucosmia)" brevis d'Orbigny. Both species, however, have Tricolia-like apertural features.
Occurrence: Middle part of Gatun formation (middle Miocene), western area, locality 170a.


Family NERITIDAE
Subfamily NERITINAE Genus Velates Montfort
Montfort, Conchyliologie syst6matique, v. 2, p. 355, 1810. 4 Type (orthotype): Velates conoideus (Nerita conoidea Lamarck=
Nerita perversa Gmelin), Eocene, Paris Basin.
Velates perversus (Gmelin), subspecies?
Plate 14, figures 5-8
Reaching a large size, ovid in ventral plan, apex moderately eccentric. Columellar lip bearing seven or. eight teeth. Callus deeply indented adjoining lower end of columellar lip and extending along inner border of outer lip, forming a wide rim.
Approximate height 60 mm, restored diameter 100 mm (largest specimen). Height 22.5 mm, diameter 43.7 mm (larger figured specimen).
Though Velates was found in limestone of the Gatuncillo formation at five localities, the only specimens showing the aperture are from locality 38 in the Rio* Casaya area. The shell of medium size shown on plate 14, figures 5, 7 is the largest of 18 collected at that locality. Twelve of the 18 have complete columellar lips, and on 9 the outer lip is preserved. The shells from locality 38, and the incomplete specimens from the other localities so far as they are preserved, closely resemble Lutetian Paris Basin specimens of Velates perversus (for citations and synonymy see Eames, 1952, p. 12). The fossils from Panama' that show the outer lip, however, have a wide rim along the inner border of the lip, whereas the rim is absent on 10 Paris Basin shells ranging in diameter from three to 70 millimeters.
Katherine V. W. Palmer has kindly called my attention to the illustrations of V. balkanicus Bontscheff (1896 [1897], p. 380, pl. 6, figs. 1-5), based on specimens from the Eocene of Bulgaria. The illustrations show a rim on the outer lip like that on the specimens from Panama. Bontscheff (1896 [1897], p. 380, pl. 6, fig. 6) also described a variety (V. balkanicus marginatus) for specimens on which the thin edge of the outer lip extends around the entire aperture, bordering the callus. The teeth of the Bulgarian fossils are heavier than those of specimens from Panamd. It is doubtful whether the rim on the outer lip is an indication of close relationship.
Velates has a range of Late Cretaceous to late Eocene. V. perversus is widely distributed in Eocene deposits from India to the Mediterranean region and the Paris Basin, reaching its acme in the middle Eocene. The genus is relatively rare in the American Eocene. Under the name V. schmideliana, V. perversus is recorded from


66







GASTROPODS: TROCHIDAE TO TURRITELLIDAE


the Yellow Limestone of Jamaica (Trechmann, 1923, p. 347, pl. 15, figs. 1-3). A similar, if not identical, form (Trechmann, 1929, p. 490, pl. 18, figs. 19a, b) and an unidentified species (Trechmann, 1924, p. 10, pl. 1, 11g. 7) have been found in other Eocene strata of that island. Fossils from California have been referred to V. perversus (Vokes, 1935, p. 382, pl. 25, figs. 1, 3, 5, pl. 26, fig. 1) and to a species of doubtful validity, V. californicus Vokes (1935, p. 384, pl. 26, figs. 3-8. A Florida locality yielded a large Velates, possibly a large Torm of V. perversus, described as V. floridanus Richards (1946; Richards and Palmer, 1953, p. 13, pl. 1, figs. 6-9). V. vokesi Cooke (1946; 1919, p. 126, pl. 5, figs. 7, 8), from the middle Eocene of the island of St. Bartholomew, is represented by poorly preserved specimens, none of which shows the aperture. The apex of V. vokesi is almost marginal, like that of V. .noetlingi Cossmann and Pissarro (Cox, 1931, p. 37). The groove on the large specimen of V. vokesi figured by Cooke and also on the small figured specimen, which is the type, evidently marks the boundary between the area where growth takes place by addition 'to the outer lip and the area where growth is the result of resorption of the callus. The boundary between these two areas on the opposite side of the shell is not apparent. A species of Velates, similar in outline to V. vokesi, is found in limestone of middle(?) Eocene age in the Sierra de Bahoruco of the Dominican Republic, and in deposits of probable middle Eocene age in Chiriqui Province, Panami and Baja California.
The remarkable architecture of Velates was described many years ago by Woodward (1892).
Occurrence: Gatuncillo formation (middle and late Eocene), Madden basin, localities 6, 7, 9, 15; Rio Casaya area, locality 38.
Genus Neritina Lamarck
Lamarck, Encyclop6die m6thodique, Histoire naturelle des vers,
v. 3, pl. 455; Liste, p. 11, 1816.
Type (logotype, Children, Lamarck's Genera of shells, p. 111,
1823): Neritina pulligera (Nerita pulligera Linn6), Recent,
rivers of India and Melanesia.
Opinion 119 of the International Commission on Zoological Nomenclature, issued in 1931, placed Neritina Lamarck, with N. pulligera as the type, in the Official List of Generic Names.
Subgenus Vitta Mdrch
M6rch, Catalogus conchyliorum * Comes de Yoldi, pt. 1,
p. 166, 1852.
Type (logotype, Baker, Acad. Nat. Sci. Phila. Proc., v. 75, p.
137, 1923): Nerita virginea Linn6, Recent, southern Florida
to northern South America, mainly estuarine.
The convex callus and color pattern suggest that the following two species may be allied to Neritina virginea. They therefore are doubtfully assigned to the subgenus


Vitta. According to Baker, in the publication just cited, Vitta is estuarine to fresh-water and is found in eastern America and western Africa.
Neritina (Vitta?) species
Small, spire worn. Callus thick, moderately convex. Columellar lip finely and weakly denticulate. Color pattern poorly preserved, consisting of dark wavy axial lines.
Height (practically complete) 7 mm, diameter (incomplete) 6 mm. Height (practically complete) 5 mm, diameter (practically complete) 5 mm.
This unidentified Neritina is represented by four incomplete specimens from the Culebra formation at locality 108c. The columellar lip is exposed on only one of them. The smallest has traces of dark axial lines and another shows such lines on a remnant of the outer calcite shell layer adjoining the edge of the callus. This Culebra species, like the following Gatun species, may be allied to the Recent Caribbean Neritina virginea (Linn6). It has a thicker callus than small specimens of that Recent species.
Occurrence: Culebra formation (early Miocene), Gaillard Cut, locality 108c.
Neritina (Vitta?) cf. N. virginea (Linn6) Plate 21, figures 1, 2
Small, spire corroded. Callus moderately thick, strongly convex. Columellar lip finely and weakly denticulate. Color pattern consisting of closely spaced minutely zigzag dark axial lines, wider at forward apex of V's (apex toward outer lip). Near outer lip and also near callus the widened apices disintegrate into isolated triangles. On later half of body whorl a solid relatively wide dark spiral band adjoins suture.
Height (incomplete, spire corroded) 3.6 mm, diameter
3.6 mm (figured specimen).
Two small shells, collected from the middle part of the Gatun formation at two localities in the western area, are referred to Neritina cf. N. virginea (Linn6).
-The color pattern is well preserved on the figured specimen. On the other, slightly larger, specimen only small patches of the outer calcite layer, and therefore of the color lines, remain. The lines evidently are not as closely spaced as on the figured specimen.
The convex callus and color pattern suggest relationship to the Caribbean Recent N. virginea, which reaches a much larger size. The most common color pattern of N. virginea consists of wavy dark lines interrupted by dark-bordered ovoid or triangular lightcolored eyes. The eyes are absent on some specimens and in some subspecies, but on Recent shells that lack eyes the lines are not as strongly zigzagged as on the figured fossil from Panam6. A specimen collected at


67







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


the type locality of Neritina (Puperita) figulopicta Maury (1917, p. 152, pl. 24, fig. 10; Cercado formation, Dominican Republic), presumably conspecific with N. figulopicta, has the callus and the prevailing color pattern of N. virginea and evidently belongs to that species.
The fossils from the Gatun formation, and also those from the Culebra formation referred to Neritina sp., may be immature shells of species as large as N. virginea, or may be mature shells of small species. As shown by numerous specimens, N. chipolana Dall (1890-1903, pt. 2, p. 422, pl. 23, fig. 19, 1892), from the Chipola formation of Florida, is a small species (height 5 millimeters) comparable in size to the fossils from Panam6. It has a color pattern of widely spaced, irregularly curved or zigzag, axial lines, or widely spaced groups of two to five such lines. The callus is thinner than that of the fossils from Panamd and is indented by a ledge adjoining the base of the columellar lip.
Occurrence: Middle part of Gatun formation (middle Miocene), western area, localities 161c, 170a.
Family THIARIDAE?
Genus Hannatoma Olsson?
Olsson, Bull. Am. Paleontology, v. 17, no. 63, p. 80, 1931. Type (orthotype): Melanatria? gesteri Hanna and Israelsky,
Oligocene, Perd.
Hannatoma? cf. H. emendorferi Olsson Plate 14, figure 3
Of small size for genus Hannatoma, Mesalia-like in outline. Preserved spire whorls preceding penult sculptured with two strong flangelike spirals, the posterior spiral adjoining the suture, the anterior spiral lying a little in front of middle of whorl. Penult bearing also a narrower spiral emerging from anterior suture. Body whorl broken; aperture and growth line unknown.
Height (incomplete) 35.5 mm, diameter (incomplete) 15 mm (figured specimen).
An incomplete silicified fossil from the Gatuncillo formation in the Rio Casaya area is doubtfully identified as a species of Hannatoma comparable to H. emendorferi, which occurs in the Eocene of Peru, in strata that were thought to be of Oligocene age when the species was described (Olsson, 1931, p. 82, pl. 15, figs. 3, 8). Unfortunately the aperture is not preserved and the growth line is not discernable. The spirals are more flangelike than those of H. emendorferi and of a closely allied, or identical, form found in strata of late Eocene age in eastern Colombia and western Venezuela.
Some species of Mesalia, including forms of the widely distributed Eocene M. fasciata (Lamarck) (Cox, 1930, p. 157, pl. 18, figs. 2, 3) have two flangelike spirals on


spire whorls. The spirals, however, are narrow and the posterior one does not adjoin the suture.
Occurrence: Gatuncillo formation (middle Eocene), Rio Casaya area, locality 38.
Family LITTORINIDAE
Genus Littorina F6russac
F6russac, Tableaux syst6matiques des arimaux mollusques, p. XI (vernacular name "littorine" for "paludines marines", five species of which are listed or p. ix-x with the designation "Paludina, marine"), p. XXXIV ["Littorine, Littorina" a& subgenus of "Paludine, Paludina, F6russ. (fluv. et marin)",
no species mentioned], 1822.
Type (logotype, de Blainviile, Dictionnaire des sciences
naturelles, v. 56, p. 98 ("le genre Littorine, ayant pour type le T. littoreus"), 1828: Turbo littoreus Linn6, Recent, western
Europe.
F6russac gave no definition of the name Littorina and cited no species under it. On other pages, however, he listed five species as marine species of Paludina and on still another page he stated that he was forming a subgenus under the name littorine for marine paludines, which constituted the genus Trochus of Adanson. These vernacular names are the same as those used oni page XXXIV with the corresponding formal names-1 This is a roundabout method, involving vernacular names, of determining what species Ferussac included under Littorina.
Littorina aff. L. angulifera (Lamarck)
Plate 16, figures 1, 2
Of medium size, high-spired. Periphery of body whorl sharply angulated at beginning of whorl, obtusely angulated toward outer lip. Narrow spiral grooveG visible on preserved parts of outer shell. Columellar lip excavated.
Height (practically complete) 12 mm, diameter 8.5, mm (figured specimen).
An imperfect specimen of the genus Littorina was found in the uppermost part of the Culebra formationin an association of brackish-water and marine species.1 Much of the shell is not preserved, including the edge of the basal and outer lips. The sculpture, however,, remains on two patches of outer shell. It shows to best advantage on the base of the body whorl adjoining the thin wash of parietal callus.
Imperfect as this fossil is, it is of exceptional interest, as it is the first Tertiary Littorina to be recorded from the Caribbean region and it extends back to the early, Miocene the lineage of a living Caribbean species, L. angulijera (Lamarck) (Bequaert, 1943, p. 23, pl. 7). The fossil so closely resembles small angulated specimens of L. angulijera that unequivocal assignment to that species may be justified. The columellar lip is wider than on most small shells of L. angulifera ex-4


68


I






GASTROPODS: TROCHIDAE TO TURRITELLIDAE


mined, but on some small shells of the Recent species it is as wide or wider.
According to Bequaert (1943, p. 24), in his recent monograph of the western Atlantic species of the genus L. angulifera is found, generally on mangroves in brackish inlets, from Florida to Brazil, on the west coast of Africa, and has reached the Pacific coast of Panam'i by transportation through the Panaml Canal. 4This species is recorded from Pleistocene deposits on the Caribbean side of the Canal Zone near Mount Hope (Brown and Pilsbry 1913a, p. 495). It is represented in three of MacDonald's Pleistocene collections from that area (USGS 5849, 5850, 5868) and also in two lots of Pleistocene fossils lie collected at and near the north end of Gatun Locks (USGS 5867, 6038).
After this report was in proof a small imperfect specimen that seems to be L. angulgifera was found in a collection from strata of middle Miocene age on Rio Banana in southeastern Costa Rica (USGS 5882f) and a large specimen, unequivocally identified as that species, was found in a collection of late Miocene fossils from Swan Cay, in the Bocas del Toro Archipelago, northwestern Panamd (USGS 8305).
Bequaert (1943, p. 3) assigned L. angulfjere to the subgenus Littoraria.
Occurrence: Uppermost part of Culebra formation (early Miocene), Gaillard Cut, locality 110.
Family VITRINELLIDAE
Studies of Recent vitrinellids have not yet progressed 'far enough to sort the genera of probably diverse affinities that are currently placed in this family. The Gatun formation yielded all the vitrinellids described in the present report.
Genus Teinostoma H. and A. Adams
H. and A. Adams, Genera of Recent Mollusca, v. 1, p. 122,
August, 1853.
Type (virtual monotype and logotype, A. Adams, Thesaurus
conchyliorum, pt. 22, p. 259, 1863): Teinostosia politm A.
Adams, Recent, Santa Elena (presumably Ecuador).
Pilsbry and McGinty (1945-50, pt. 1, p. 1, 1945) have pointed out that Teiinostoma was virtually monotypic, as T. anomalum C. B. Adams, the only species mentioned other than T. politun, was a nude name.
No known Caribbean fossil species has the characters of the subgenus Teinostoma s.s.: greatly depressed shell and spoutlike extension of the peristome.
Subgenus Idioraphe Pilsbry
Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 73, p. 398, 1922. Type (orthotype): Teinostoma angulatum (Gabb) (Cyclops angulatus Gabb), Miocene, Dominican Republic.
It has been claimed that the spire of Teinostoma s.s. is concealed by overlap of the body whorl (Woodring, 1928, p. 444) and that it is not concealed (Pilsbry and 413788-57--6


Olsson, 1941, p. 47). As a matter of fact, it has become evident that both statements are justified (Pilsbry and Olsson, 1945-52, p. 38, 1952). The typical form of the type species, known only from Arthur Adams' descriptions and illustrations, reproduced by Pilsbry and Olsson (1945-52, p. 251, pl. 22, fig. 6, 1945; p. 38, pl. 2, figs. 1, la, 1b, 1952), has an exposed spire. A form from the Gulf of California, so similar in essential features to T. politum that it was described as T. politum ultimum (Pilsbry and Olsson, 1945-52, p. 252, pl. 22, figs. 1, la, 1b, 1945), has a concealed spire. In other words, the subgenus Idioraphe, which has a concealed spire, is not as sharply set off as it was once thought to be. Idioraphe also resembles Teinostoma s.s. in having a thick shell, thick callus, and thick enamel. Nevertheless Idioraphe is a useful name for small teinostomes that have a concealed spire, are not strongly depressed, and lack the spoutlike extension of the peristome characteristic of T. politurn.
Teinostoma (Idioraphe) spermatia Woodring, n. sp.
Plate 17, figures 19-24, 31-33, 37-39
?Teinostoma cf. carinatum d'Orb., Toula, K. k. Geol. Reichsanstalt Jahrb., Band 61, p. 497, pl. 31, fig. 10, 1911 (Miocene, Canal Zone).
Small, thick-shelled, depressed but somewhat domeshaped. Periphery bluntly angular on early part of body whorl, narrowly rounded on later part. Tip of spire exposed, remainder concealed by overlap of body whorl. Entire spire concealed by enamel on very large specimens. Umbilical and parietal callus thick and completely coalesced.
Height 0.7 mm, diameter 1.8 mm (type); height 1.1 mm, diameter 2.6 mm (large form, figured).
Type: USNM 561312; paratypes, Stanford Univ.
Type locality: 147b (USGS 6033c, Panama Railroad, about 3,500 feet (1,065 m) southeast of Gatun railroad station, Canal Zone), middle part of Gatun formation.
Teinostoma spermatia is the most widespread teinostome in the middle part of the Gatun formation and is particularly abundant at the type locality, where several hundred specimens were collected. It is represented, however, by only one specimen from the upper part of the formation, and none was found in the lower part.
Immature shells (pl. 17, figs. 22-24) are more nearly circular than mature shells. Furthermore the outer lip of immature shells ascends almost to the tip of the spire and therefore has a different outline from that of mature shells. Three specimens from the type locality, one of which is illustrated (pl. 17, figs. 19-21), show faint to fairly strong microscopically punctate spiral striae. This sculpture is doubtless a normal character, but is ordinarily concealed by enamel. The three


69







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


specimens that show it have thin enamel, except on the later part of the body whorl, where the sculpture gradually disappears under the thicker coat of enamel. Fourteen specimens from the type locality that are assigned to T. spermatia are exceptionally large as compared with scores of apparently mature specimens, like the type. As shown on plate 17, figure 31, the tip of the spire of this relatively large form is covered with a thin glaze of enamel. These 14 large specimens, which do not intergrade with the much more abundant smaller apparently also mature form, may represent a different species. If so, however, immature shells of the large and the small species have not been distinguished and apparently are indistinguishable.
Species more or less closely resembling Teinostoma spermatia have been living in American waters since Eocene time. The very similar T. tectispira (Pilsbry, in Olsson and Harbison, 1953, p. 417, pl. 50, figs. 6-6c), a Pliocene species from Florida, has no trace of spiral sculpture. T. spermatia is more depressed and more elongate in dorsal outline than T. angulatum (Gabb) (Pilsbry, 1922, p. 398, pl. 37, figs. 1, la, 1b), and even the large form of T. spermatia is a little smaller. T. angulatum, which is found in the Cercado formation of the Dominican Republic, has very faint closely spaced spiral striae. Species similar to T. spermatia are living in both western Atlantic and eastern Pacific waters. T. cryptospira (Verrill) (Bush, 1897, p. 118, figs. 1, 2) ranging from Cape Hatteras to Florida, is more circular in dorsal outline. T. cecinella Dall (1919, p. 369), a species from Lower California, is more elongate in dorsal outline, larger, and has a thicker shell.
Toula's Teinostoma cf. T. carinatum may be T. spermatia, though his illustrations show an exposed spire and a peripheral carina. Pilsbry (in Olsson and Harbison, 1953, p. 415), however, thought it is very similar to the Recent T. carinatum (d'Orbigny).
Occurrence: Middle and upper parts of Gatun formation (middle Miocene). Middle part, eastern area, localities 146, 147b, 147f, 147g, 147h, 147i (identification doubtful), 153a. Upper part, eastern area, locality 177.
Teinostoma (Idioraphe) angulatum trochalum Woodring, n.
subsp.
Plate 17, figures 4-6
Small, moderately depressed, dome-shaped. Periphery moderately angular on early part of body whorl, rounded on later part. Spire partly concealed by overlap of body whorl and glaze of enamel. Umbilical and parietal callus thick and coalescing.
Height 1 mm, diameter (incomplete) 1.7 mm (type).
Type: USNM 561431; paratypes, Stanford Univ.


Type locality: 137 (USGS 16911, Transisthmian. Highway, 1.7 km northwest of Sabanita, Panamd), lower part of Gatun formation.
This teinostome, found in the lower part of the Gatun,4 formation, is considered a small race of T. angulatum (Gabb), the type of Idioraphe, from the Miocene of the Dominican Republic (Pilsbry, 1922, p. 398, pl. 37, figs. 1, 1a, 1b). Gabb's specimens were collected at an unknown locality in the Dominican Republic. Specimens from the Cercado formation-Maury's T. sandomingense, (Maury, 1917, p. 156, pl. 24, fig. 24)-evidently are conspecific, although the early part of the body whorl" of the type has a more sharply angulated periphery. T. angulatum trochalum is smaller and lacks spiral sculpture. T. umbilicatum (Lea) (Mansfield, 1930, p. 134, pl. 20, figs. 1-3) and other Tertiary species from southeastern United States, as well as the Recent T. cryptospira (Verrill), have a less angular periphery.
Occurrence: Lower part of Gatun formation (middle! Miocene), localities 136a, 137, 138a.
Subgenus Aepystoma Woodring, n. subgen.
Type: Teinostoma (Aepystoma) andrium Woodring, n. sp., Miocene, Gatun formation, Panam6 and Canal Zone.
Of medium size, thick-shelled, spire moderately de-. pressed, exposed. Smooth or sculptured with punctate fine spiral striae. Umbilical and parietal callus thick, more or less coalesced. Callus filling umbilicus on mature shells.
The subgeneric name Aepystoma is proposed for a group of thick-shelled teinostomes that have an exposed spire and callus-filled umbilicus. Fossil and Recent Panamic species allied to Teinostoma andrium have been assigned to the subgenus Pseudorotella by Pilsbry and Olsson. Pseudorotella, however, has a smaller and thinner shell and less depressed spire.
Teinostoma (Aepystoma) andrium Woodring, n. sp.
Plate 17, figures 40-42; plate 18, figures 9-11
Of medium size, thick-shelled, dorsal surface slightly domed. Periphery rounded on later part of body whorl, faintly and bluntly angular on early part. Sculpture of microscopically punctate faint spiral striae, for most part concealed on body whorl of mature specimens by glaze of enamel. Umbilical and parietal callus thick and coalescing.
Height 2 mm, diameter 4.7 mm (type).
Type: USNM 561315; paratype, Stanford, Univ.
Type locality: 137 (USGS 16911, Transisthmian Highway, 1.7 kin northwest of Sabanita, Panam ), lower part of Gatun formation.
Teinostoma andrium is by far the largest of the Gatun teinostomes. The sculpture is distinct only on early


70






GASTROPODS: TROCHIDAE TO TURRITELLIDAE


whorls. The umbilicus of immature shells is not completely filled with callus (pl. 17, fig. 41).
T. andrium is closely related to T. caroniense Maury i1925, p. 249, pl. 43, figs. 3, 4), a late Miocene species from Trinidad, but has a flatter columellar lip and flatter rmbilical callus. The recent Ecuadorean T. millepunctatum Pilsbry and Olsson (1945-52, p. 253, pl. 23, figs. 1, la, 1b, 1945) has more coarsely punctate spirals, and is smaller and thinner. The Recent western Panamic T. imperfectum Pilsbry and Olsson (194552, p. 254, pl. 22, figs. 2, 2a, 2b, 1945) also is smaller and thinner, and has a thin, narrow umbilical callus.
Occurrence: Lower and middle parts of Gatun foriation (middle Miocene). Lower part, locality 137. Middle part, eastern area, locality 147i.
Subgenus Pseudorotella Fischer
Fischer, Jour. Conihyliologie, t. 6, p. 52, 1857.
Type (monotype): Pseudorotella semistriata (d'Orbigny) (Rotella
semistriata d'Orbigny), Recent, Cuba.
Pseudorotella is used in the present report for small, smooth or spirally sculptured teinostomes that have a moderately thick shell, exposed relatively high spire, wide umbihical callus filling-or not quite filling-the
-umbilicus, and narrow parietal callus. This usage may be found to be inappropriate when specimens of the type species are available. The type species has fine spiral striae above the periphery, according to dOrbigny's illustrations.
As suggested by Pilsbry and McGinty (1945-50, pt. 1, p. 2, 1945), subgeneric rank is preferable to the generic rank that has been assigned to Pseudorotella (Woodring, 1928, p. 445). The Miocene Jamaican "Pseudorotella'' homala Woodring (1928, p. 447, pl. 38, figs. 13-15) represents a minor group of teinostomes, more closely related to Aepystoma than to Pseudorotella, characterized by a bicarinate truncated periphery and relatively strong spiral sculpture.
Teinostoma (Pseudorotella) pycnum (Woodring)
Plate 17, figures 25-27
Pseudorotella pycna Woodring, Carnegie Inst. Washington Pub.
385, p. 446, pl. 38, figs. 10-12, 1928 (Miocene, Jamaica).
Small, moderately thick-slielled, periphery rounded. Body whorl pinched against suture, producing a suggestion of a sutural collar, corresponding to faint gutter between outer lip and parietal callus. Umbilical callus thick, filling umbilicus. Parietal callus narrow, its edge sharply defined.
Height 0.8 mm, diameter 1.3 mm (figured specimen).
Type: USNM 135502.
Type locality: Bowden, Jamaica, Bowden formation (middle Miocene).


The faint sutural collar and narrow parietal callus are characteristic features of Teinostoma pycenum. The few specimens from the Gatun formation are slightly smaller than the type. T. vitreum (Gabb) (Pilsbry, 1922, p. 399, pl. 37, figs. 3, 3a, 3b), from the Cercado formation of the Dominican Republic, lacks the faint sutural collar. T. parvicallum Pilsbry and McGinty (1945-50, pt. 1, p. 4, pl. 2, fig. 2, 1945), a Recent teinostome from Florida, is slightly larger and has a higher spire.
Occurrence: Lower and middle parts of Gatun formation (middle Miocene). Lower part, locality 138. Middle part, eastern area, locality 147b. Bowden formation (middle Miocene), Jamaica.
Teinostoma (Pseudorotella) stemonium Woodring, n. sp.
Plate 17, figures 1-3
Small, moderately thick-slielled, periphery rounded, but marked by a spiral thread. Body whorl somewhat pinched against suture. Whorls smooth between suture and periphery. Periphery and base near periphery sculptured with four or five relatively heavy spiral threads (three or four on immature shells). Umbilical callus completely, or not quite completely, filling umbilicus. Parietal callus narrow, overlapping umbilical callus. Junction of outer lip and parietal callus forming a faint gutter.
Height 1 mim, diamter 1.5 mm (type).
Type: USNM 561432. Paratype, USNM 561433. Paratypes, Stanford Univ.
Type locality: 138a (Stanford Univ. locality 2656, Transistlinian Highway 1.6 ki northeast of Canal Zone boundary, Panamr'; same as USGS 16909), lower part of Gatun formation.
This sculptured Pseudorotella is represented by nine specimens collected by T. F. Thompson from the lower part of the Gatun formation. It seems to have no known close allies.
Occurrence: Lower part of Gatun formation middlee Miocene), locality 138a.

Subgenus Diaerecallus Woodring, n. subgen.
Type: Teinsoira (Diaerecallus) sychrni Woodring, n. sp.
lriocene, Gatun formation, Canal Zone.

Small, thick-slielled, smooth or practically smooth. Suture strongly impressed. Umbilicus filled with callus, Edge of umbilical callus forming well defined ridge. Extension of parietal callus overlapping umbilical callus, deeply grooved adjoining coluiellar lip.
Diaerecallus is characterized by the strongly impressed suture and the abrupt overlap of a grooved extension of the parietal callus. It may represent a modification of Aepystoma, or possibly of a teinostome more or less


71







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


similar to the subgenus Annulicallus Pilsbry and McGinty (1945-50, pt. 4, p. 17, 1946; type (orthotype): Teinostoma carinicallus Pilsbry and McGinty, Recent, Florida). Annulicallus has a sharp ridge at the edge of the umbilical callus, which is concave.
Teinostoma (Diaerecallus) sychnum Woodring, n. sp.
Plate 17, figures 28-30
Small, thick-shelled, periphery rounded. Apical whorl large for size of shell. Very faint microscopic spiral striae visible on penult or earlier whorls of some specimens. Umbilical callus bounded by ridge, which is overlapped by extension of parietal callus. Extension of parietal callus deeply grooved adjoining outer lip.
Height 1.1 mm, diameter 1.7 mm (type). Height
1.6 mm, diameter 2.2 mm (largest specimen).
Type: USNM 561316.
Type locality: 147b (USGS 6033c, Panama Railroad, about 3,500 ft (1,065 m) southeast of Gatun railroad station, Canal Zone), middle part of Gatun formation.
The curious callus, shown by four specimens from the type locality, at first glance suggests abnormality. The extension of the parietal callus is formed at a late growth stage. It is missing on three immature shells from the type locality and also on an immature shell from locality 155a, the only specimen from that locality. These immature shells resemble the subgenus Aepystoma, but have a low ridge at the edge of the umbilical callus. The large apical whorl and strongly impressed suture of this species are noteworthy features. No close fossil or living allies are known.
Occurrence: Middle part of Gatun formation (middle Miocene), eastern area, localities 147b, 155a.
Genus Anticlimax Pilsbry and McGinty
Subgenus Anticlimax s.s.
Pilsbry and McGinty, Nautilus, v. 60, p. 12, 1946. Type (logotype (Pilsbry and McGinty, Nautilus, v. 59, p. 77,
1946) of Climacia Dall, 1903 (not M'Lachlan, 1869), renamed Climacina Aguayo and Borro, 1946 (not Gemmellaro, 1878), renamed Anticlimax): Teinostoma (Climacia) calliglyptumn
Dall, Pliocene, Florida.
Perhaps Anticlimax, the second name proposed in rapid succession as replacement of the homonym Climacia, was not intended to be as derisive as it sounds. It recalls some of Jousseaume's names.
Teinostoma (Climacia) calliglyptum was virtually the monotype of Climacia. Dall used that combination in a list of fossils and in the explanation of a plate (Dall, 1890-1903, pt. 6, p. 1,610, 1,633, 1903). He also used the combination Teinostoma (Climacia) radiata Dall in the same list of fossils. There is, however, no indication that he intended that name for his Collonia


radiata, no matter how unequivocal his intention proves to be.
The species of Anticlimax have recently been reviewed by Pilsbry and Olsson. The genus is strongly domeshaped and has axial folds or undulations of varying strength on the base of the shell. The subgenus Anticlimax s. s. is characterized by a narrow callus on. the columellar lip, from which a ridge spirals up the widely open umbilicus. The earliest species occurs in the early Miocene Thomonde formation of Haiti. A Recent species is found in the Caribbean Sea and another possibly off Florida, but none so far in thePanamic region.


Anticlimax (Anticlimax) gatunensis Pilsbry and Olsson
Plate 18, figures 5-7


4


Anticlimax gatunensis Pilsbry and Olsson, Bull. Am. Paleontology, v. 33, No. 135, p. 7, pl. 2, figs. 5, 5a, 5b, 1950 (Miocene,
PananA).
Dome-shaped, base flattened. Peripheral carina a relatively wide thin ledge. Upper surface sculptured with weak spiral striae, which disappear near periphery and on upper surface of peripheral ledge are replaced by microscopic axial threads. Base bearing 13 heavy axial folds. Outer half of base, including base of peripheral ledge, sculptured with spiral striae. Ridge bordering umbilicus moderately narrow.
Height 1.7 mm, diameter (incomplete) 3 mm (figured specimen).
Type: Acad. Nat. Sci. Phila. 18401.
Type locality: Cut on Boyd-Roosevelt (Transisthmian) Highway, just below bridge over Rio Cativa and about 3% miles from road junction at Margarita,, Panami (same as USGS 16909) lower part of Gatun formation.
The figured specimen, a topotype, has a damaged peristome and carina. It is the only specimen in the U. S. National Museum collections; two smaller specimens are in the Stanford University collection from the same locality. The flattened base and wide peripheral carina are the most characteristic features of this species. These features distinguish it from the most closely related species, A. schumoi (Vanatta) (1913, p. 24, pl. 2, figs. 2, 7), a Recent species from British Honduras. A. derbyi (Maury) (1917, p. 156, pl. 24, fig. 20), the only other described Miocene species of Anticlimax s.s., occurs in the Cercado formation of the Dominican Republic and in the Thomonde formation of Haiti. It has a more swollen base, narrower peripheral ledge, fewer and heavier folds on the base, and no spiral striae on the base.
Occurrence: Lower part of Gatun formation (middle Miocene), localities 138, 138a.


72






GASTROPODS: TROCHIDAE TO TURRITELLIDAE


Subgenus Subclimax Pilsbry and Olsson
Pilsbry and Olsson, Bull. Am. Paleontology, v. 33, No. 135, p. 5, 1950.
rype (orthotype): Anticlimax hispaniolensis Pilsbry and Olsson, Miocene, Dominican Republic.
Subclimax, which is somewhat intermediate between Anticlimax s.s. and dome-shaped species of Teinostoma, has the umbilicus partly or completely closed by a wide umbilical callus. It has, however, axial undulations or folds of varying strength on the base, like those of Anticlimax s. s. The earliest species, occurring in the early Miocene Baitoa formation of the Dominican Republic, is of the same age as the earliest species of Anticlimax s. s. Subclimax is living in the western Atlantic and the eastern Pacific.

Anticlimax (Subclimax) teleospira hystata Woodring, n. subsp.
Plate 18, figures 1-3
Dome-shaped, base slightly inflated. Periphery bluntly angular, except near outer lip, where it is drawn out into a ledge. Upper surface sculptured with faintly punctate spiral striae, which are indistinct or absent on middle third of body whorl and near outer lip. Base sculptured with faintly punctate spiral striae that disappear near umbilical margin and toward aperture, except on peripheral ledge. Base also bearing faint crude axial undulations. Umbilical callus filling umbilicus, except a narrow niche adjoining parietal callus. Junction of outer and basal lips drawn out in an ,angular thickened spoutlike projection, broken on type.
Height 1.5 mm, diameter (incomplete) 2.7 mm
-(type).
Type: USNM 561319.
Type locality: 185 (USGS 8383, Caribbean coast, west of Rio Miguel, station 26 plus 100 feet (30 m) Panamd), upper part of Gatun formation.
Anticlimax teleospira hyslata is represented by two ,specimens from the upper part of the Gatun formation in the coastal area west of the Canal Zone. The spoutlike projection of the peristome is like the projection of the type of Teinostoma. It is broken on the type but preserved on the other specimen, which is otherwise less complete. A. teleospira proper (Pilsbry and Olsson, 1950, p. 10, pl. 2, figs. 7, 7a), which occurs in the lower part of the Gatun formation but is not represented in the U. S. National Museum collections, has a carinate periphery and stronger basal undulations.
The closely related A. tholus (Pilsbry and MeGinty) (1945-50, pt. 3, p. 79, pl. 8, figs. 1, la, 1b, 2, 2a, 1946), a Recent species from Florida, has stronger spiral sculpture and lacks the extended peristome. An undescribed species, dredged at a depth of 6 to 9 fathoms off Beaufort, N. C., has a more angular periphery,


73


narrower umbilical callus, and lacks the extended peristome. A. willetti Hertlein and Strong (1940-51, Pt. 10, p. 112, pl. 9, figs. 13-15, 1951), from the Pacific coast of Costa Rica, is larger and has stronger basal undulations. The only other recorded Miocene species of Subclimax, A. hispaniolensis Pilsbry and Olsson, has a sunken apex and axial undulations on the upper surface of the body whorl. Both Gatun species of Anticlimax are more similar to Recent species than to contemporaneous or slightly older Miocene species in the Caribbean region so far described.
Occurrence: Upper part of Gatun formation, western area (late Miocene), locality 185.

Genus Cyclostremiscus Pilsbry and Olsson
Pilsbr and Olsson, Acad. Nat. Sci. Phila. Proc., v. 97, p. 266,
1945.
Type (ortlhotype): Vitrinella panamesis C. B. Adams, Recent,
Pacific coast of Panamd.
Subgenus Ponocyclus Pilsbry
Pilsbry, Acad. Nat. Sci. Phila. Mon. 8, p. 426, 1953. Type (orthotype): Adeorbis beauii Fischer, Recent, Florida and
West Indies.
Ponocyclus lacks the axial sclptaire of the subgenus Cyclostremiscus s. s. Some species, however, are more or less intermediate and Pilsbry realized that the name Ponocyclus may eventually be found to be superfluious.
Cyclostremiscus (Ponocyclus) pentagonus (Gabb) Plate 17, figures 7-15
Cyclostrema pentagona Gabb, Am. Philos. Soc. Trans., n. ser.,
v. 15, p. 243, 1873 (Miocene, Dominican Republic).
Vitrinella pentagona (Gabb), Gabb, Acad. Nat. Sci. Phila. Jour.,
2d ser., v. 8, p. 368, pl. 47, fig. 68, 1881 (Miocene, Dominican
Republic).
Cyclostrema quadrilineatum Toula, K. k. Geol. Reiclusanstalt
Jahrb., Band 61, p. 497, pl. 31, figs. 1la-e, 1911 (Miocene,
Canal Zone).
Circulus pentagona (Gabb), Pilsbry, Acad. Nat. Sci. Phila. Proc.,
v. 73, p. 397, 1922 (Miocene, Dominican Republic).
'Circulus" pentagonus (Gabb), Woodring, Carnegie Inst. Washinagton Pub. 385, p. 441, pl. 37, figs. 16-18, 1928 (Miocene,
Jamaica).
Small, depressed, wlhorls 4%, the first 2% very slowly enlarging. Protoconch relatively large, rising abruptly. Body whorl bicarinate or, less conmmonly, tricarinate. Early whorls rounded between sutures. A carina appears on later half of penult about midway between sutures and forms upper carina on body whorl. Basal carina generally weaker than upper. Periphery rounded, bluntly angular (the usual condition), or sharply angular, forming a third carina. A few specimens have one or more faint spiral threads on penult above carina, and a few have a low spiral thread on body whorl below and near upper carina or above and near lower carina. Umbilical wall bearing crude gen-






GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


erally faint spiral cords more or less roughened by growth threads. Upper part of peristome gently arched forward.
Height 1 mm, diameter 1.6 mm (figured bicarinate specimen). Height 1.1 mm, diameter 2.3 mm (figured large specimen).
Type: Acad. Nat. Sci. Phila. 2831.
Type locality: Dominican Republic, Miocene.
This small Cyclostremiscus occurs throughout the Gatun formation. It is rare in the lower part, rare to abundant in the middle part, and rare in the upper part. Several hundred specimens were collected from the middle part at locality 147b.
These fossils show a considerable range of variation in the outline of the body whorl, in the presence or absence of spiral threads near the upper and lower carinae, and in the strength and coarseness of the spiral cords facing the umbilicus. The usual form is bicarinate (pl. 17, figs. 7-9). Though tricarinate shells (pl. 17, figs. 10-12) are not common in the middle part of the Gatun formation, the few specimens from the lower and upper parts (one and two, respectively) are tricarinate. Spiral threads, generally faint, near the upper and lower carinae are exceptional. The umbilical spirals generally are weak. They are, however, exceptionally strong on the large specimen shown on plate 17, figures 13-15. This large specimen, collected from the middle part of the Gatun formation, shows a further modification in the rounded outline of the body whorl. At the beginning of the body whorl of this specimen the upper carina is moderately strong, the basal carina is weak, and the peripheral angulation is faint. These carinae and angulation rapidly disappear. This specimen is larger than the bicarinate and tricarinate forms. Inasmuch as mature bicarinate and tricarinate forms are rounded near the peristome, the exceptional features of the rounded specimen are presumably correlated with its size. Toula's illustrations, however, show a shell of moderate size, the body whorl of which is rounded at an early stage.
Cyclostremiscus pentagonus occurs in the Cercado formation of the Dominican Republic and in the Bowden formation of Jamaica. The few available specimens from the Dominican Republic and Jamaica are tricarinate. It was formerly thought that the Gatun form could be differentiated by the weak sculpture on the umbilical wall (Woodrmg, 1928, p. 441). That sculpture, however, is too variable for consistent differentiation.
Closely related forms are living in the western Atlantic and the eastern Pacific. "Circulus" trilix (Bush) (1897, p. 127, pl. 22, figs. 6, 10, 10a, 12, pl. 23, figs. 10, 15), ranging from Cape Hatteras to Cuba, is consistently tricarinate and enlarges more rapidly, so


that with the same number of whorls (about 4/) Recent shells are almost twice as large. Recent shells and' those from the Gatun formation have the same kind of protoconch and aperture. Inasmuch as the degree of enlargement is the only character now apparent t8 differentiate Recent shells and tricarinate fossils, treat4 ment of "C." trilix as a subspecies of C. pentagonusi appears to be preferable. Fossils from the early' Miocene Chipola formation and the middle Miocene Shoal River formation of Florida have been referred to "Circulus" trilix (Gardner, 1926-47, p. 600, 1947), These Florida fossils are tricarinate and are larger than those from the Gatun formation.
"Circulus" cerrosensis Bartsch (1907, p. 173, figs. 9a, b, c), which ranges from Santa Catalina Island, Cali-. fornia, to Baja California and the Gulf of California, and probably to Panamd, is the eastern Pacific analog of "Circulus" trilix. It has not been determined, whether Pacific and Atlantic shells can consistently be distinguished. Relatively strong spiral cords facing the umbilicus are more common in the few lots of Pacific shells. Shells from both oceans that are still lustrous show under strong light very faint miicroscopic spiral lineation. It is doubtful whether Cyclo-! stremiscus glyptomphalus Pilsbry and Olsson (1945-52, p. 67, pl. 7, fig. 3, 1952), a Pleistocene form from the Pacific coasts of western Panami, can be distinguished from "Circulus" cerrosensis. Pilsbry and Olsson suggested the probability of local races of a widely spread species. Cyclostremiscus glyptobasis Pilsbry and Olssoq, (1945-52, p. 66, pl. 7, figs. 4, 4a, 1952), also from the Pleistocene of western Panama, probably is a variety, or subspecies, of "C." cerrosensis with a sculptured bas.. The Ecuadorean form "Circulus" cosmius Bartsch (1907, p. 173, figs. 8a, b, c) also is closely allied to' "Circulus" cerrosensis, but is characterized by a slight downward bending of the upper margin of the peristome I where it extends forward. Though the peristome of the type of "Circulus" cosmius is damaged, four speci mens in the type (and only) lot have a perfect peristome. The seven specimens in the type lot have very weak umbilical sculpture. "Circulus" occidentalis Pilsbry and Olsson (1941, p. 48, pl. 9, fig. 3), from the Pliocene of Ecuador, shows downward bending of the peristome and should be compared with "Circulus" cosmius.
Cyclostremiscus tricarinatus (C. B. Adams) (Pilsbry and Olsson, 1945, p. 271, pl. 28, figs. 3, 3a, 3b), living on the Pacific coast of Panama, is similar to the tri, carinate species so far mentioned. It has, however, faint axial riblets between the periphery and suture, and therefore is intermediate between Ponocyclus and Cyclostremiscus s.s.
Occurrence: Lower, middle, and upper parts of Gatun formation (middle and late Miocene). Lower-


74


I





GASTROPODS: TROCHIDAE TO TURRITELLIDAE


i part, localities 138, 138a. Middle part, eastern area, localities 146, 147b, 147f, 147g, 147h, 153a, 155c; ovestern area, locality 161. Upper part, eastern area, locality 173; western area, locality 185. Cercado and nGurabo formations (middle Miocene), Dominican ]Republic. Bowden formation (middle Miocene), Jamaica.
Genus Solariorbis Conrad
Conrad, American Jour. Conch., v. 1, p. 30, 1865. [Type (logotype, Dall, Wagner Free Inst. Sci. Trans., v. 3, pt. 2,
p. 414, 1892): Delptinsla depressa Lea, Eocene, Alabama.
Subgenus Solariorbis s.s.
The subgenus Soliariorbis s. s. is characterized by relatively large size, faint spiral sculpture (microscopically punctate in the type species), and a wide umbilical wall on the body whorl adjoining the aperture.
Solariorbis (Solariorbis) strongylus Woodring, n. sp.
Plate 17, figures 43-45
Of medium size, thick-shelled, moderately depressed. Periphery faintly and bluntly angulated, except at and near peristome where it is rounded. Penult and part of preceding whorl sculptured with closely spaced spiral threads. Spirals become faint and even disappear on body whorl, but most persistent near suture and just above periphery. Under strong light base shows barely discernible microscopic spiral striation. Umbilicus moderately narrow, asymmetrical, bounded by a crude spiral ridge, which is slightly roughened by growth wrinkles. Parietal callus thin.
Height 1.3 mm, diameter 2.4 mm (type). Height
1.5 mm, diameter 3 mm (largest specimen).
Type: USNM 561322; paratypes, Stanford Univ.
Type locality: 138 (USGS 16909, Transisthmian Highway, 1.6 kilometers northeast of Canal Zone boundary, Panam ), lower part of Gatun formation.
The weak sculpture and moderately narrow asymmetrical umbilicus are characteristic features of this species. It is represented by 13 specimens, all from the type locality.
Occurrence: Lower part of Gatun formation (middle Miocene), localities 138, 138a.

Subgenus Hapalorbis Woodring, n. subgen.
Type: Circulus liriope Bartsch, Recent, Gulf of California.
The name Hapalorbis is proposed for a minor group of Solariorbis consisting of small carinate species that have a narrow umbilical wall on the body whorl adjoining the aperture. The type species has a spiral thread above and below the peripheral carina-formmg thread. Others have one to three threads below the periphery and one or two above. Still others have none below or above the periphery.


The subgenus Systellomphalus (Pilsbry and Olsson, 1941, p. 48; type (orthotype): Systellomphalus perornatus Pilsbry and Olsson, Pliocene, Ecuador), with which Pilsbry and Olsson associated species closely allied to "Circulus" liriope, may be defined as embracing species that have axial riblets on spire whorls and axial wrinkles on the base of the body whorl adjoining the umbilicus.
Hapalorbis is not known to have survived the Miocene in Caribbean waters.
Solariorbis (Hapalorbis) hyptius hyptius Woodring, n. sp. and n.
subsp.
Plate 17, figures 16-18
Small, thick-shelled, depressed, body whorl increasing rapidly in diameter. Periphery sharply or moderately carinate, except at and near peristome. Umbilicus very narrow, asymmetrical. Umbilical wall very narrow, the angulated umbilical border being inserted almost flush with base of body whorl where it emerges from umbilicns. Parietal callus moderately thick.
Height 0.7 mm, diameter 1.4 mm (type).
Type: USNM 561323; paratypes Stanford Univ.
Type locality: 147b (USGS 6033c, Panama Railroad, about 3,500 feet (1,065 meters) southeast of Gatun railroad station, Canal Zone), middle part of Gatun formation.
The very narrow and asymmetrical umbilicus, and very narrow umbilical wall are conspicuous and characteristic features of this species. It is closely related to the type of Hapalorbis: "Circulus'' liriope Bartsch (1911, p. 231, pl. 40, figs. 7-9), which is represented by the type and an imperfect specimen, both dredged at a depth of 21 fathoms off La Paz, Lower California. The fossils are smaller, more depressed, have a smaller more asymmetrical umbilicus and narrower umbilical wall, and lack a spiral thread above and below the peripheral carina.
Solariorbis hyptius proper was found in the lower and middle parts of the Gatun formation, but is rare except at the type locality. The 68 specimens collected at the type locality and the 2 additional specimens from the middle part of the Gatun have remarkably uniform characters. The five specimens from the lower part, however, are not so sharply carinate and reach a slightly larger size.
Occurrence: Lower and middle parts of Gatun formation (middle Miocene). Lower part, locality 138a. Middle part, localities 146, 147b, 147f.
Solariorbis (Hapalorbis) hyptius anebus Woodring, n. subsp.
Plate 17, figures 34-36
Resembling S. hyptius proper, but larger and umbilicus correspondingly larger. Peripheral carina flanked above and below by a narrow low spiral thread.


75







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


Height 0.9 mm, diameter 1.5 mm (type).
Type: USNM 561324.
Type locality: 185 (USGS 8383, Caribbean coast, west of Rio Miguel, Panama), upper part of Gatun formation.
This subspecies is based on two specimens from the upper part of the Gatun formation. Though the spirals flanking the periphery are narrower and lower than those of "Circulus" liriope, the sculptural pattern is the same, suggesting close relationship. As indicated by the name, however, alliance with the smaller Hapalorbis from the middle part of the Gatun formation is thought to be closer. Both Solariorbis hyptius proper and S. hyptius anebus have a depressed outline and very narrow umbilical wall, whereas "Circulus" liriope is less depressed and has a wider umbilical wall.
A Pliocene species from Ecuador, "Pseudorotella" lens Plisbry and Olsson (1941, p. 47, pl. 9, fig. 2; 194552, p. 51, 1952) has the same sculptural pattern as Solariorbis hyptius anebus and "Circulus" liriope, but has a heavy callus facet almost closing the umbilicus and is sculptured with two spiral threads above the periphery, The Recent Panamic "Vitrinella" seminuda C. B. Adams (Pilsbry and Olsson, 1945-52, p. 278, pl. 27, figs. 3, 3a, 3b, 1945; p. 51, 1952) lacks spirals above the periphery.
Occurrence: Upper part of Gatun formation (middle and late Miocene), eastern area, locality 173, western area, locality 185.
Genus Episcynia Mdrch
M6rch, Malakozool. Bldtter, Band 22, p. 155, 1875. Type (monotype): Architectonica (Episcynia) inornata (d'Orbigny)
(Solarium inornatum d'Orbigny), Recent, West Indies.
In the western Atlantic Episcynia ranges from North Carolina to Brazil, and in the eastern Pacific from Santa Cruz Island, Calif., to Peru. Miocene species from Florida and the Caribbean region are the earliest known.
Episcynia megalia Woodring, n. sp.
Plate 18, figures 4, 8
Large, thin-shelled, whorls 5. Suture shallow, located on peripheral carina of preceding whorl, even at peristome. Peripheral carina minutely and irregularly roughened by exaggerated growth wrinkles. Similar growth wrinkles adjoin suture on later part of body whorl. Umbilical half of base and umbilical wall sculptured with more strongly emphasized growth wrinkles. Upper half of umbilical wall also sculptured with two narrow spiral threads that disappear near peristome. Umbilical border sharply angular.
Height 2.7 mm, diameter 5.3 mm (type).
Type: USNM 561325.


Type locality: 138 (USGS 16909, Transisthmian Highway, 1.6 kilometers northeast of Canal Zone boundary, Panama), lower part of Gatun formation.
Episcynia megalia, which is based on one specimen from the lower part of the Gatun formation, is the largest Episcynia so far described. It is most closely related to two species living in the eastern Pacific: E.nicholsoni (Strong and Hertlein) (1939, p. 241, pl. 22, figs. 2-4; Panama) and the closely allied E. bolivari Pilsbry and Olsson (1946, p. 11, pl. 1, figs. 6-8; Colombia and Peru; Pleistocene, western Panami). On both Recent forms the carina is exposed on the later whorls of the spire. E. nicholsoni evidently is more depressed than E. megalia, and E. bolivari has a slight angulation on the body whorl above the periphery.
E. naso (Pilsbry and Johnson) (Pilsbry, 1922, p. 379, pl. 37, figs. 5, 5a), the only other described fossil species from the Caribbean region (Miocene, Dominican Republic and Jamaica), has strong regularly spaced, serrations on the peripheral carina.
Occurrence: Lower part of Gatun formation (middle Miocene), locality 138.
Family RISSOIDAE
Subfamily RISSOINAE
Genus?
"Alvania" aff. "A." epulata (Pilsbry and Johnson)
Minute, rapidly enlarging. Protoconch very large for size of shell, consisting of 2% rapidly enlarging smooth whorls. Remaining 2% whorls sculptured with closely spaced axial ribs (17 on body whorl), between which are closely spaced spiral threads. Base sculptured with three wider and more widely spaced spirals. Outer lip varicose, its interior inaccessible.
Height 1.2 mm, diameter 0.7 mm.
Two minute specimens, both found by T. F. Thompson in the Gatun formation, are the only rissoids. They evidently are conspecific and are closely allied to "Rissoa" epulata Pilsbry and Johnson (Pilsbry, 1922, p. 384, pl. 34, fig. 5), a Miocene species from an unknown locality in the Dominican Republic. That species is narrowly umbilicate. The specimen from the lower part of the Gatun formation is immature and has a narrow umbilical groove, but the mature specimen from the upper part of the formation, of approximately the same dimensions as the type of "Rissoa" epulata, is completely nonumbilicate.
Rissoids more or less similar to the Gatun species are generally referred to the genus Alvania (Risso, 1826, p. 140; logotype, Nevill, 1884 [1885], p. 105, Alvania europea Risso= Turbo cimex Linn6, Recent, Mediterranean). The type of Alvania is four times as large, and has a relatively much smaller protoconch, coarser sculpture, and lirations on the interior of the outer lip.


76







GASTROPODS: TROCHIDAE TO TURRITELLIDAE


One or more of the numerous generic and subgeneric names proposed for European, Australian, and Neozelanic rissoids may possibly be suitable for "Alvania' aff. "A." epulata.
Nevill's designation for the type of Alvania-"type A. cimex Lin. [as Alv. curopaea Risso]"-appears to be the earliest valid designation. It has the same effect as numerous designations of Turbo cimex Linn6 and the much later designation of Alvania freminvillea Risso, also a synonym of Turbo cimex (Gordon, 1939, p. 29).
Occurrence: Lower and upper parts of Gatun formation (middle Miocene). Lower part, locality 136a (1 immature). Upper part, eastern area locality 173 (1 mature, protoconch crushed during examination).

Family RISSOINIDAE
Genus Rissoina d'Orbigny
d'Orbigny, Voyage dans l'Amnrique M6ridionale, t. 5 (Mollusques), p. 395, 1840.
Type (monotype): Rissoina inca d'Orbigny, Recent, Perd and
Chile.
Subgenus Zebinella Mrch
Mtrch, Malakozool. Blatter, Band 23, p. 47, 1876. Type (logotype, von Martens, Zool. Record, 1876, p. 30, 1877):
Rissoina decussala (Montagu) (Helix decussata Montagu), Recent, West Indies and Florida (described as a British
species).
Rissoina (Zebinella?) species
A poorly preserved altered shell from the Culebra formation is assigned to Rissoina on the basis of outline and sculpture. The outer lip and aperture are not preserved. The sculpture, consisting of narrow axial ribs and fine spiral threads between the ribs, suggests the subgenus Zebinella.
Occurrence: Culebra formation (early Miocene), Gaillard Cut, locality 99b.
Subgenus Phosinella Mdrch
M6rch, Malakozool. Bitter, Band 23, p. 51, 1876. Type (logotype, Nevill, Hand list of Mollusca in the Indian
museum, pt. 2, p. 73, 83, 1885): Rissoina pulchra (C. B.
Adams) (Rissoa pulchra C. B. Adams), Recent, West Indies.
Rissoina (Phosinella) oncera Woodring, n. sp.
Plate 23, Figure 3
Small, slender. Protoconeh of 3)( smooth rapidly enlarging whorls, the last half whorl obscurely angulated. Sculpture reticulate; axial ribs slightly wider than spiral threads. Four spirals at beginning of penult, five on later half. Outer lip strongly varicose. Fa-siolelike swelling on base strongly inflated.
Height 4.3 mm, diameter 1.7 mm (type).
Type: USNM 561332.
Type locality: 177c (USGS 5855, west side of Panama Railroad, opposite Mount Hope cemetery, Canal Zone), upper part of Gatun formation.


77


The type (and only) specimen of this species was collected from the upper part of the Gatun formation at Mount Hope. It is closely allied to R. guppyi Cossmann (Woodring, 1928, p. 366, pl. 28, fig. 10), which occurs in the Bowden formation of Jamaica and in the Cercado and Gurabo formations of the Dominican Republic, but has a more widely expanding protoconch, slightly narrower spirals on the early whorls, more inflated fasciolelike swelling, and wider space between the swelling and the lowest spiral. The Recent West Indian and Florida species identified by Dall (1890-1903, pt. 2, p. 343, 1892) as R. cancellata Philippi has a smaller protoconcb, coarser sculpture, and less inflated fasciolelike swelling.
Occurrence: Upper part of Gatoin formation (middle Miocene), eastern area, locality 177c.

Family XENOPHORIDAE
Genus Xenophora Fischer von Waldheim
Fischer (von Waldheims(, Mus6um-Demidoff, t. 3, p. 213, 1807. Type (logotype, Harris, Catalogue of Tertiary Mollusca in the
British Museum; pt. 1, Australasian, p. 253, 1897): Xenophora laevigata Fischer [von Waldheim] ("Trochus conchyliophorus Gmel., Bose, Born") = Trochus conchyliophorus Born, Recent,
West Indies.
Unidentified species of Xenophora are represented by two molds from the Gatuncillo formation and an incomplete mold from the Culebra formation.

Xenophora delecta (Guppy)
Plate 22, figures 1, 2,4
Phorus agglutinans (Lamarck), Gabb, Am. Philos. Soc. Trans.,
n. ser., v. 15, p. 241, 1873 (Miocene, Dominican Republic). Phorus delecta Guppy, Geol. Soc. London Quart. Jour., v. 32, p.
529, pl. 28, fig. 10, 1876 (Miocene, Dominican Republic). Xenophora delecta (Guppy), Maury, Bull. Am. Paleontology, v.
5, no. 29, p. 134, pl. 23, figs. 8, 9, 1917 (Miocene, Dominican Republic). Pilsbry, 1922, Acad. Nat. Sci. Phila. Proc., v. 73, p. 385, pl. 32, figs. 7, 8, 1922 ("dilecta" by error; Mliocene, Dominican Republic). Woodring, Carnegie Inst. Washington
Pub. 385, p. 376, pl. 30, figs. 3, 4, 1928 (Miocene, Jamaica). Xenophora conchyliophora (Born), Maury, Bull. Am. Paleontology, v. 5, no. 29, p. 133, pl. 23, fig. 7, 1917 (Miocene, Dominican
Republic).
Xenophora aff. trochiforom is (Born), Rutsch, Schweizer. Palaeont.
Gesell. Abh., Band 54, no. 3, p. 48, pl. 2, figs. 2, 3, 1934
(Miocene, Venezuela).
Moderately large, widely umbilicate. Spire low, periphery somewhat extended. Sculpture above periphery, between agglutinated shells and shell fragments, consisting of strongly protractive irregularly rippled threads. Base sculptured with niore uniform rippled arcuate threads parallel to columeller lip, which is broken back.
Height 25 nim, diameter (incomplete) 46 mm (figured specimen).






GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


Type: British Mus. (Nat. Hist.), Geol. Dept., Geol. Soc. London 12842.
Type locality: Dominican Republic, Miocene.
An incomplete Xenophora, found by T. F. Thompson in the upper part of the Gatun formation at Stanford University locality 2654 near Fort Davis, is referred to X. delecta. The attached shells and shell fragments with one exception (a fragment of the body whorl of a Phos-like gastropod, attached by the exterior surface) consist of pelecypods, Aequipecten being most abundant. These pelecypods and pelecypod fragments are concave side upward, also with one exception: a fragment of a mature Aequipecten scissuratus.
The generally open umbilicus and relatively strong sculpture differentiate X. delecta from the only Recent species in the Caribbean region, X. conchyliophora (Born). The Gatun fossil is widely umbilicate. On specimens of comparable size from the Dominican Republic the umbilicus is narrower and even reduced to a narrow groove. Rutsch's illustration of a specimen from the late Miocene Punta Gavilin formation of Venezuela also shows only a narrow groove.
The type of X. delecta is a small specimen, like specimens from the Gurabo formation in the collections of the U. S. National Museum (maximum diameter 24 mm). Two imperfect shells from the Cercado formation are even smaller. The Bowden formation of Jamaica also has yielded only small specimens (maximum diameter 19 mm). The ripples on the base of these small specimens, from both the Dominican Republic and Jamaica, are so strong that they form nodes. Pilsbry figured two large specimens (diameter 51 and 56 mm) that are in Gabb's collection of fossils from the Dominican Republic, and Maury illustrated, under the name X. conchyliophora, a large specimen from the Gurabo formation.
X. textilina Dall (Gardner, 1926-47, p. 561, pl. 58, figs. 31, 32, 1947), of the Chipola formation of Florida, evidently is an early form of X. delecta. It is umbilicate, but its sculpture is not as strong as that of X. delecta. The larger of the two syntypes figured by Gardner is herewith designated the lectotype. The widely umbilicate strongly sculptured fragment from the Shoal River formation, doubtfully recorded as X. textilina, is indistinguishable from X. delecta. It might, however, be the high-spired subspecies of X. delecta, X. delectafloridana Mansfield (1930, p. 121, pl. 18, figs. 5, 6), which occurs in upper Miocene deposits in western Florida.
X. delecta left no descendents in the Caribbean or Panamic regions. It is closely related, however, to X. senegalensis Fischer, a Recent west African species, and its close Recent Mediterranean ally, X. crispa "K6nig" Bronn, which occurs in rocks of late Miocene and


Pliocene age in Italy. X. delecta has somewhat coarser sculpture than those species.
The Recent Caribbean X. conchyliophora has a long history in the southeastern states and is one of the few Recent species recognized in the Eocene of that region. The Recent Panamic X. robusta Verrill, characterized by the deep orange-brown parietal callus and adjoining inner half of the interior of the body whorl, is better, treated as a subspecies of conchyliophora.
Occurrence: Upper part of Gatun formation (middle Miocene), eastern area, locality 173. Cercado and Gurabo formations (middle Miocene), Dominican Republic. Bowden formation (middle Miocene), Jamaica.' Punta Gavildn formation (late Miocene), Falc6n, Venezuela.
Family HIPPONICIDAE Genus Hipponix Defrance
Defrance, Jour. Phys. Chim. Hist. Nat. Arts, t. 88, p. 217, 1819. Type (logotype, Gray, Zool. Soc. London Proc., p. 157, 1847):
Patella cornucopia (Patella cornucopia Lamarck), Eocene, Paris Basin.
Hipponix species
The Gatuncillo fossils from the Rio Casaya area include a small presumably immature Hipponix, shaped like a wide cornucopia. Some growth lamellae are' exaggerated and there is a faint suggestion of fine radial sculpture. The muscle scar is not discernible.
Length (not quite complete) 9 mm, width 7.5 mm, approximate height 6.5 mm.
So far as this small specimen goes, it suggests a! miniature replica of the type species of the genus.
Occurrence: Gatuncillo formation (middle Eocene), Rio Casaya area, locality 38.
Family HIPPONICIDAE?
Hipponix? species
A poorly preserved limpet-shaped fossil from the Culebra formation is doubtfully referred to Hipponix. It is moderately large and elongate, and the apex is near the posterior end. The apex is worn and practically smooth. Preserved parts of the outer shell are sculptured with crude radial ribs overriden by crude concentric threads. The interior is inaccessible.
Approximate dimensions: length 21 mm, width 17 mm, height 9 mm.
If this fossil is an Hipponix, it is more similar to the Pacific H. pilosus (Deshayes) (an earlier name for H. barbatus Sowerby) than to Caribbean Recent species. H. pilosus ranges from California to Ecuador and the Galapagos, and is found in the western Pacific. It is recorded from the Miocene of the Dominican Republic (Pilsbry, 1922, p. 384).
Occurrence: Culebra formation (early Miocene), Gaillard Cut, locality 108c.


78








Family CREPIDULIDAE
Genus Crepidula Lamarck
Lamarck, Soc. Hist. Nat. Paris Mem., p. 78, 1799. Type (monotype): Patella fornicata Linn6, Recent, eastern United States.
Molds from the Culebra formation are identified as Crepidula sp.

Crepidula of. C. maculosa Conrad Plate 19, figures 4, 5
Crepidula galunensis Toula, K. k. Geol. Reichsanstalt Jahrb.,
Band 61, p. 498, pl. 31, figs. 12a, b, 1911 (Miocene, Canal
Zone).
Of medium size, moderately narrow, moderately vaulted. Protoconch of small specimens consisting of about 1)% whorls of neritoid outline. Deck of small specimens moderately deep seated, bearing a wide shallow median indentation.
Length 28.5 mm, width 17.5 mm, approximate height 10.5 mm (figured specimen).
A species of Crepidula from the Gatun formation is comparable to the Recent C. maculosa, to which attention has recently been called (Stingley, 1952). As pointed out by Stingley, C. maculosa has a pedal muscle scar adjoining the adapical insertion of the deck and the edge of the deck has a very slight median indentation, whereas the better known and more northern C. fornicaoa (with which C. maculosa has been confused) lacks the muscle scar and has a pronounced median indentation.
The only fairly large shell from Gatun (pl. 19, figs. 4, 5) is attached to a crab carapace and the interior is inaccessible. Owing presumably to inequalities on the carapace, this shell has two faint depressions and correspondingly modified growth lines. The other shells (all of which are small, ranging in length from 1.5 to 12 millimeters) evidently represent the same species as the fairly large specimen. Two that are moderately small show the muscle scar of C. maculosa.
According to Toula's description and illustration, C. gatunensis was based on a small shell (length 2.8 millimeters) like those in the collections at hand. That name is available, should the name C. maculosa be found to be inappropriate for the fossils.
Though C. fornicata is recorded from the Miocene of Trinidad (Maury, 1925, p. 244), it is unlikely that that species lived in the Caribbean Sea at any time.
Occurrence: Lower, middle, and upper parts of Gatun formation (middle Miocene). Lower part, localities 137, 138. Middle part, eastern area, localities 147b, 155c, 157. Upper part, eastern area, locality 178.


79


Crepidula plan Say
Plate 19, figures 1-3
Crepidula plana Say, Acad. Nat. Sci. Phila. Jour., 1st ser. v. 2
p. 226, 1822 (Recent, Maryland to Florida). Dall, Wagner Free Inst. Sci. Trans., v. 3, pt. 2, p. 318, 1892 (Miocene to Recent, eastern United States). Brown and Pilsbry, Acad.
Nat. Sci. Phila. Proc., v. 63, p. 360, 1911 (Miocene, Canal Zone). Brown and Pilsbry, idem, v. 65, p. 495, 1913 (Pleistocene, Canal Zone). Pilsbry, idems, v. 73, p. 385, 1922 (Miocene, Dominican Republic). Olsson, Bull. Am. Paleontology, v. 9, no. 39, p. 159, 1922 (Miocene, northwestern Panamd). Gardner, U. S. Geol. Survey Prof. Paper 142, p. 0565, 1947 (Miocene, Florida); see this publication for other
citeios.
Crypta fornicala (Linn), Gabb, An. Philos. So. Trans., v. 15,
p. 242, 1873 (_Miocene, Dominican Republic).
Of medium size, narrow, compressed, flat or concave. Protoconeh of immature shells consisting of 1% to 1Y2 rapidly enlarging whorls of neritoid outline, destroyed at later stage by encroachment of aperture. Deck bearing a moderately deep narrow abapical marginal indentation and a moderately deep very wide median indentation.
Length 15 mm, width 10.5 mm, height 2 mm (larger figured specimen).
Slipper limpets recovered from the apertures of Gatun coiled gastropods agree closely with the Recent Crepidula plana. All the fossils were found in the lower part of the formation. C. plan is already recorded from the Gatun formation of the Canal Zone and from late Miocene strata in northwestern Panama'.
A species of Crepidula that has a similar outline and similar deck characters is living in the eastern Pacific Panamic region. It presumably is C. nivea C. B. Adams, but is generally known as C. numsaria Gould. The few specimens of this species from Panamd in the collection of the U. S. National Museum have slightly deeper deck indentations than C. plan.
Occurrence: Lower part of Gatun formation (middle Miocene), localities 137a, 138, 138a. Middle part of Gatun formation (middle Miocene), eastern area (Brown and Pilsbry). Late Miocene, Water Cay, Panama. Miocene, Dominican Republic. Early to late Miocene, Maryland to Florida. Pliocene, North Carolina to Florida. Pleistocene, Massachusetts to Florida, Canal Zone. Recent, Prince Edward Island, Canada, to Texas and the West Indies.
Family Calyptraeidae
The genus Cheilea is not represented in the collections at hand. Cheilce princetonia Browli and Pilsbry (1911, p. 360, fig. 2), based on an internal and external mold from the Gatun formation, may be conspecific with the Cheilea from the Bowden formation of Jamaica


GASTROPODS: TROCHIDAE TO TURRITELLIDAE







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


identified as the Recent Caribbean form designated C. equestris (Linn6) (Woodring, 1928, p. 375, pl. 30, figs. 1, 2).
Genus Calyptraea Lamarck
Lamarck, Soc. Hist. Nat. Paris M6m., p. 78, 1799. Type (monotype): Patella chinensis Linn6, Recent, western
Europe.
An unidentified small Calyptraea that has an eccentric apex is represented by poorly preserved specimens from the marine member of the Bohio(?) formation at Vamos Vamos.
Calyptraea cf. C. aperta (Solander)
Molds of a relatively large, relatively high-spired Calyptraea from the Gatuncillo formation of Madden basin are comparable to C. aperta, which is widely distributed in the Eocene and Oligocene of western Europe and southeastern United States. (For citation and synonomy see Palmer, 1937, p. 145.) In tropical America C. aperta, or a comparable form, is recorded from the Paleocene of Trinidad and the Eocene of Colombia and Perd.
Occurrence: Gatuncillo formation (late Eocene), localities 9, 12.

Calyptraea centralis (Conrad)
Infundibulum centralis Conrad, Am. Jour. Sci., 1st ser., v. 41,
p. 348, 1841 (Miocene, North Carolina, p. 343). Conrad, Fossils of the Medial Tertiary of the United States, No. 3 (Fossils of the Miocene formation of the United States), p. 80,
pl. 45, fig. 5, 1845 (Miocene, North Carolina).
Trochita sp. indet., Gabb, Am. Philos. Soc. Trans., v. 15, p. 242,
1873 (Miocene, Dominican Republic).
?Trochita collinsii Gabb, Acad. Nat. Sci. Phila. Jour., 2d ser.,
v. 8, p. 342, pl. 44, figs. 11, Ila, 1881 (Miocene, Costa Rica). Calyptraea centralis (Conrad), Dall, Wagner Free Inst. Sci.
Trans., v. 3, pt. 2, p. 353, 1892 (Miocene to Recent).
Maury, Acad. Nat. Sci. Phila. Jour., 2d ser., v. 15, p. 100, pl. 13, fig. 6, 1912 (Miocene, Trinidad). Maury, New York Acad. Sci., Scientific Survey of Porto Rico and Virgin Islands, v. 3, pt. 1, p. 48, 1920 (Miocene, Puerto Rico). Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 73, p. 385, 1922 (Miocene, Dominican Republic). Maury, Bull. Am. Paleontology, v. 10, no. 42, p. 243, pl. 43, fig. 2, 1925 (Miocene and Pliocene, Trinidad). Gardner, U. S. Geol. Survey Prof. Paper 142, p. 562, pl. 56, figs. 3-5, 1947 (Miocene, Florida); see this
publication for other citations.
?Calyptraea cf. centralis (Conrad), Hubbard, N. Y. Acad. Sci.,
Scientific Survey of Porto Rico and Virgin Islands, v. 3, pt. 2, p. 133, 1920 (Miocene, Puerto Rico). Maury, 1925, Brasil Serv. Geol. Mi. Mon. 4, p. 65, pl. 1, figs. 5, 10, 1925 (Miocene
Brazil).
Of medium size, circular in ventral plan, apex central. Protoconch of about 1 strongly inflated, rapidly enlarging whorls. Free edge of platform convex forward; reflected columellar edge not closely appressed, forming a relatively high umbilicuslike opening.


Maximum diameter 16 mm, height 6 mm (largest specimen).
Type: Apparently lost.
Type locality: Natural Well, N. Car., Duplin formation (late Miocene).
Specimens from the Culebra formation, identified as Calyplraea cf. C. centralis, are comparable in size and outline to C. centralis, but none shows the interior. All are molds, with the exception of one, which was collected at locality 108c and has much of the shell preserved.
The description is based on specimens from the lower part of the Gatun formation. The only large specimen, from locality 138, is imperfect. The interior of the only specimen from the middle part of the Gatun formation is inacessible. It is listed as Calyptraea cf. C. centralis.
The Gatun fossils that show the interior agree closely with topotypes of C. centralis collected at Natural Well, N. Car. As pointed out by Dall and Gardner, Recent specimens are smaller than those from the Miocene. Recent specimens in the collection of the U. S. National Museum, representing localities from Cape Hatteras to the West Indies, are not more than a third the size of large Miocene fossils. Two large Recent shells, however, are exceptions. One, which has a maximum diameter of 11.5 millimeters, was cataloged at an early date and is labelled "West Indies." The other (maximum diameter 15.5 millimeters) was in the Henderson collection and is labelled "Marco, Florida." The reflected edge of the platform of both is closely appressed, like that of the western European C. chinensis, the type of the genus. They probably are specimens of that species with erroneous locality data. Should a name be desirable for the small Recent race, it may be designated Calyptraea centralis candeana (d'Orbigny), as indicated by Dall's synonymy. Pliocene fossils from the Caloosahatchee marl of Florida have a maximum diameter of 10 millimeters and therefore are intermediate in size.
The Recent Panamic C. mamillaris Broderip is larger than C. centralis, and has a thicker shell and mottled brown color pattern.
Occurrence: Culebra formation (early Miocene; Calyptraea cf. C. centralss, Gaillard Cut, localities 99b, 99c, 100, 108c, 11Oa. Lower and middle parts of Gatun formation (middle Miocene); lower part, localities 137, 138, 138a; middle part, eastern area, locality 147j, (Calyptraea cf. C. centralis). Early Miocene, Puerto Rico, ?Costa Rica, ?Brazil. Late Miocene(?), Trinidad. Miocene, Dominican Republic. Early to late Miocene, Maryland to Florida. Pliocene, Trinidad, Florida. Recent (small race) Cape Hatteras to West Indies.
Genus Trochita Schumacher
Schumacher, Essai d'un nouveau systeme des habitations des vers testacas, p. 57, 184, 1817.


80







GASTROPODS: TROCHIDAE TO TURRITELLIDAE


Type (logotype, Reheder, Biol. Soc. Washington Proe., v. 56,
p. 41, 1943): Trochila spiralis Schumacher (=Trochus radians Lamarck= Turbo trochiforios Born), Recent, Ecuador to
Chile.
Trochita has a thick shell, distinct suture, and moderately strong to strong radial sculpture. The free edge of the platform is convex forward, except at the distal margin, where it bears a narrow identation. The ':columellar edge of the platform is reflected only at its insertion. On adult shells this short reflected border is molded on the platform, like callus. The genus and its species were discussed by Rehder (1943) in the publication cited for the type designation.
Trochita heretofore has not been recorded from the Caribbean region. It is now extinct there, and in the western Atlantic is limited to the Falkland Islands and the coast of Argentina. Though it occurs in the Miocene and Pliocene of California, in the eastern Pacific it is i now found only south of the equator. The survival of the genus in west African waters-a genus otherwise confined to the Peruvian, Magellanic, and South African provinces-is nore readily understood in view of its occurrence in the Miocene of the Caribbean region and in the Pliocene and Pleistocene of west Africa. The West African species is considered conspecific with the Miocene Caribbean fossil and the Recent eastern Pacific species. It is an expectable fossil in the West African Miocene.
Trochita trochiformis (Born)
Plate 19, figures 11-14
Turbo trochiforis Born, Index Musei Caesarei Vindobonensis'
p. 355, 1778 (sole citation: Knorr, pt. 3, pl. 29, figs. 1, 2, 1768,
"Antillean Islands").
Trochus radians Lamarck, Encyclop6die mthodique, Histoire
naturelle des vers, t. 3, pl. 445, figs. 3a, b; Liste, p. 10, 1816.
Lamarck, Histoire naturelle des aniaux sans vertlbres, t. 7,
p. 11, 1822 (Recent, mer des Antilles").
Calyptraca (Trochatella) trochifornis (Gmelin), d'Orbigny, Voyage dans 1'Amdrique Muridionale, t. 5, pt. 3, 1c. 461, pl. 59, fig. 3, 1841 (Recent, Chile, Perd; Calyptraea radians in explanation of plate). Nickles, Manuels Ouest-Africains, t. 2, p. 73, fig. 99, 1950 (Recent, Angola). Lecointre, Morocco Service Gtologique, Notes et 6m. 99, t. 2, p. 108, pl. 25, figs. 1-4,
1952 (Pleistocene, MIorocco).
Infndibulu trochiforcce (Gicelin), d'Orbigny, Voyage dans
l'Anirique M6ridionale, t. 3, pt. 4 (Paltontologie), p. 158,
1842 (Pleistocene, Chile).
Trochila radians (Lamarck), Reeve, Conchologia Iconica, v. 11,
Trochita, pl. 1, species 3, 1859 (Recent, Chile). Sowerby, Thesaurus Conchyliorum, v. 5, p. 64, pl. 451, figs. 95, 96, 99, 1883 (ltecent, Chile). Relider, Biol. Soc. Washington Proc.
v. 56, p. 42, 1943 (Recent, Ecuador to Chile); see this publication for other citations and synonymy.
Calyptraea (Trochita) trochiforsits (Gmelin), Grant and Gale,
San Diego Soc. Natural History Mem., v. 1, p. 795, pl. 31, fig. 11, 1931 (Miocene and Pliocene, California; RecentPanamil to Perd).


Trochatella trochiformis (Gmelin), Lecointre, Jour. Conchyliologie, t. 90, p. 240, unnumbered pl., fig. 2, 1950 (Pliocene,
Pleistocene, Morocco).
Of medium size, moderately low spired or moderately high spired, apex broken. Sculpture consisting of heavy crude axial ribs. Platform broken back to insertion.
Maximtuim diameter 28.8 mm, height (incomplete) 10.7 mm (smaller figured specimceen). Maximum diameter 43.5 ncm, height (almost complete) 27 mm (larger figured specimen).
This calyptraeid is represented by two specimens from the lower part of the Gatun formation, both collected by T. F. Thompson. Though the interior of the larger specimaen is inaccessible and the platform of the smaller is broken far back, they are identified with considerable confidence as Trochita trochijormis. The middle part of the Gatun formation in the western area at locality 151 yielded a wor thicek-shelled apical fragment listed as Trochita? sp. Incomplete and poorly preserved fossils from the middle member of the Caimito formation in the Gatun Lake area and the Culebra formation suggest that the lineage of T. trochiformis can be traced back to the late Oligocene. None of these Caimito and Culebra fossils, however, is unequivocally identified.
Trochita trochijormis now ranges from 'Manta, Ecuador, to Valparaiso, Chile. It is low spired to high spired. On low-spired shells the platform is almost flush with the base of the shell; on high-spired shells it is a considerable distance above the base. The heavy crude axial ribs are characteristic. The largest Recent specimen i the collection of the U. S. National Museum has a maximum diameter of 65 millimeters.
A small form of Trochita trochiformis (recorded as T. radians) occurs in formations of Pliocene age i California as far north as the Santa Maria district (Arnold aced Anderson, 1907, p. 60, pl. 21, fig. 1; Woodring and Bramlette, 1950 [1951], p. 72, pl. 13, fig. 19), in Santa Barbara County. Early and middle Xciocene forms from California have been identified as Trochita costellata Conrad (Eldridge and Arnold, 1907, p. 148, pl. 32, fio-. 3; Locl and Corey, 1932, p. 268, pl. 63, fig. 11), and late Miocecce forms have been named "Calyptraca" diabloensis Clark (1915, p. 485, pl. 70, fig. 9) and "Calyptraea" ioartini Clark (1915, p. 486, pl. 70, fig. 8). As suggested by Grant and Gale, these heavily ribbed Miocene forms, ranging in age from early to late Miocene, are probably to be referred to Trochita trochiformis. The inadequate type material of Trochita costellata Conrad (1857b, p. 195, pl. 7, fig. 3) consists of two molds showing traces of relatively fine ribs. Additional specimens from the type locality (Gaviota Pass in the western Santa Ynez Moiuntains, Santa Barbara


81







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


County, Calif.) have not been described and the age is still unknown.
I am indebted to R. T. Abbott for pointing out that Born's Turbo trochiformis is an earlier name for Lamarck's Trochus radians.
Occurrence: Middle member of Caimito formation (late Oligocene), Gatun Lake area, localities 57 (Trochita? sp.), 57a (Trochita cf. T. trochijormis). Culebra formation (early Miocene), Gaillard Cut, localities 115a (Trochita? cf. T. trochiformis), 115b (Trochita cf. T. trochiformis, 116 (Trochita cf. T. trochiformis). Lower part of Gatun formation (middle Miocene), locality 136, 136a. Middle part of Gatun formation (middle Miocene), western area, locality 161c (Trochita? sp.). Miocene, California (identification doubtful). Pliocene, California, Morocco. Pleistocene, Chile, Cape Verde Islands, Morocco. Recent, Manta, Ecuador, to Valparaiso, Chile; Cape Verde Islands, Angola.
Genus Crucibulum Schumacher
Schumacher, Essai d'un nouveau systeme des habitations des
vers testac6s, p. 56, 182, 1817.
Type (logotype, Burch, Conchological Club Southern Calif.
Proc., no. 56, p. 19, 1946): Crucibulum planum Schumacher (=Patella auricula Gmelin), Recent, Florida and West Indies.
J. E. Gray's (1847, p. 157) designation of Patella auriculata as the type of Crucibulum is not valid in the strict sense, as Patella auriculata was not mentioned by Schumacher. Schumacher, however, based Crucibulum planum on Chemnitz's Patella auriculata without mentioning it by name. Both Crucibulum planum and Patella auriculata, given binomial standing by Dillwyn in the year when Schumacher published the generic name Crucibulum, are synonyms of Patella auricula Gmelin.
The recent type designation by Burch, on the advice of Keen, appears to be the first valid designation. The question of possible virtual monotypy, raised by Keen, need not be considered. Whatever the status of Crucibulum rugoso-costatum, the only other species mentioned by Schumacher, may be, Crucibulum was not monotypic.
Unidentified molds from the Culebra formation, the Alhajuela sandstone member of the Caimito formation, and the Chagres sandstone are listed as Crucibulun sp.
Subgenus Crucibulum s. s.
Crucibulum (Crucibulum) chipolanum Dall
Plate 19, figures 6, 7
Crucibulum auricula var. chipolanum Dall, Wagner Free Inst. Sci. Trans., v. 3, pt. 2, p. 349, 1892 (Miocene, Florida). Crucibulum chipolanum Dall, Gardner, U. S. Geol. Survey Prof. Paper 142, p. 567, pl. 56, figs. 10, 11, 1947 (Miocene, Florida).


Of medium size, elliptical in ventral plan. Protoconch of about 1Y rapidly enlarging whorls. Shell smooth to diameter of 1%Y to 3 mm. At that stage the shell is elliptical and the apex lies far to the rear. Sculpture consisting of closely spaced crudely roughened radial ribs, some of which bifurcate and a few of which unite as they extend outward. Right anterior border of cup sharply angulated, joined to side of shell at level far above ventral margin of cup.
Maximum diameter 27 mm, height 16.5 mm (figured specimen).
Type (lectotype, the specimen figured by Gardner): USNM 112783.
Type locality: USGS 2212, Tenmile Creek, Fla., Chipola formation (early Miocene).
Specimens from the middle part of the Gatun formation at the Gatun Third Locks excavation closely resemble Crucibulum chipolanum in characters of protoconch, sculputre, and cup. The right side of the cup of the figured specimen was uncovered, but the shell is too fragile to uncover the entire cup. Locality 155c yielded a worn incomplete specimen. It shows the same kind of cup and traces of radial ribs, but is only tentatively identified as C. chipolanum.
C. chipolanum was described as a variety of the Recent Caribbean C. auricula (Gmelin). Undoubtedly it is closely related to that species and to the Recent Panamic C. spinosum (Sowerby). The cups of all three are similar. The sculpture of C. auricula is weaker and more varied than that of C. chipolanurn. As pointed out by Gardner, the protoconch whorls of C. auricula are wider and emerge more obtusely. Both C. auricula and C. spinosum are recorded from the Miocene of the Dominican Republic (Pilsbry, 1922, p. 385).
A species of Crucibulum from the Shoal River formation of Florida and its Oak Grove sand member, C. chipolanum dodoneum Gardner (1926-47, p. 567, pl 56, figs. 18-20, 1947), has coarser sculpture than C. chipolanum. It presumably is not closely related, however, to C. chipolanum, as its cup is attached to the side of the shell at the level of the ventral margin of the cup.
Dall designated no type material for C. chipolanun. In his description he mentioned only one locality: the Chipola River, a mile below Baileys Ferry. He also examined and identified, however, specimens from the nearby Tenmile Creek locality, a mile west of Baileys Ferry. The specimen from the Tenmile Creek locality figured by Gardner is herewith designated the lectotype.
Occurrence: Middle part of Gatun formation (middle Miocene), eastern area, localities 155, 155b, 155c (including a doubtfully identified worn specimen). Chipola formation (early Miocene), Florida.


82







GASTROPODS: TROCHIDAE TO TURRITELLIDAE


Subgenus Dispotaea Say
Say, Acad. Nat. Sci. Phila. Jour., 1st ser., v. 4, p. 131, 1824. Type (logotype, Olsson and Harbison, Acad. Nat. Sci. Phila.
Mo:. 8, p. 276, 1953): Calyptraea costata Say, Miocene,
Maryland.
After describing Calyptraea grandis, Say remarked that it does not properly belong in the genus Calyptraea and therefore proposed to place it in a new genus Dispotaea. He then assigned two other species to Dispotaea: Dispotaea tubifera, a new Recent species from South America, and his previously described 'Oalyptraea costata (Say, 1820, p. 40; see p. 38 for locality data), a fossil species from Upper Marlborough, Maryland, associated with others now known to be Miocene. The types of these three species evidently are lost. So far as known Dispotaca tubifera has not been recognized. Calyptraea costata has been interpreted in different ways by Dall (1890-1903, pt. 2, p. 349, 1892) and Martin (1904, p. 244, pl. 58, figs. 7a, b). Dall thought it is the strongly costate Crucibulum that occurs in the St. Marys formation of Maryland and assigned it varietal rank under Crucibulum auricula, the type of Crucibulum. According to Martin, it is the weakly costate Crucibulum found in the Calvert formation of Maryland. Martin's interpretation is reasonable in view of the locality cited by Say and in view of Say's statement that the cup is attached by one side to the wall of the shell. At all events Martin's identification is accepted.
Olsson and Harbison, apparently not realizing that Say assigned the unequivocally identifiable Calyptraea grandis to Dispotaea, recently designated Calyptraea costate as the type of Dispotaea. The cup of Dispotaca is attached by the right side, or part of the right side, to the interior of the shell. The type species has a wide attachment area; Crucibu?um grande has an attachment area of varied width. The Recent Crucibulum striatum (Say) (Nova Scotia to Florida), which has been cited as the type of Dispotata by several authors, has a consistently wide attachment area.

Crucibulum (Dispotaea) springvaleense Rutsch Plate 19, figures 8-10
?Capulus? gatunensis Toula, K. k. Geol. Reichsanstalt Jahrb.,
Band 58, p. 692, pl. 25, fig. 1, 1909 (Miocene, Canal Zone).
Brown and Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 63, p. 360,
1911 (Toula's record).
Capulus? sp., Toula, K. k. Geol. Reichsanstalt Jahrb., Band 58, p. 692, pl. 25, fig. 2, 1909 (Miocene, Canal Zone). Crucibulum (Dispotaca) gatunense (Toula), Anderson, Calif. Acad. Sci. Proc., 4th ser., v. 18, no. 4, p. 121, pl. 13, figs. 4-6, 1929 (Miocene, Canal Zone, Colombia). Crucibulen? springvaleense Rutsch, Naturf. Gesell. Basel Verhandl., Band 54, p. 138, pl. 4, fig. 8, 1942 (Miocene, Trinidad).


83


Of medium size, circular to elliptical in ventral plan. Protoconch of 1)) to 1Y rapidly enlarging whorls. Shell smooth to a diameter of 3 to 6 mm. Shell at that stage circular and apex central or subeentral. Sculpture consisting of heavy widely spaced radial ribs, the interspaces bearing crude concentric lamellae, or consisting of closely spaced, generally narrower roughened and pitted irregular ribs. Right side of cup widely attached to interior of shell.
Maximum diameter 19.2 mm, height 11 mm (figured specimen). Maximum diameter 24.5 mm, height 14 mm (largest specimen).
Type: 518/190 Basel Natural History Museam.
Type locality: Springvale quarry, Trinidad, Springvale formation (late Miocene).
Crucibulum springvaleense is widely distributed in the Gatun formation. Though the interior of the Trinidad specimens, on which this species was based, is unknown, the Crucibulum from Panamd is unequivocally identified. Coarsely sculptured specimens have the external characters of a topotype of C. springvaleense kindly forwarded by Dr. Rutsch. Some fossils from PanamA have only regular coarse sculpture, others only irregular generally finer sculpture, and still others, like tle specimen figured, a coesbination of both.
This species has left no descendants in the Caribbean region. It appears to be allied, however, to the Recent Panamic Crucibulum pectinatum Carpenter, which has fewer ribs than the coarsely sculptured typical form of C. springvaleense. C. pectinatum ranges from the southern part of the Gulf of California to Panama, possibly to Perd.
It is unlikely that Crucibuluin springvaleense is the species Toula described as Capulus? gatuneesis. At a diameter of 11.5 millimeters, the greatest diameter of the type of Capulus? gatunensis, it should show traces of strong sculpture, if it were the Crucibulun. According to a communication from Dr. Rutsch, who examined the types of Toula's Gatun gastropods, the type of Capulus? gatunensis is an unidentifiable mold retaining parts of the inner shell layer. In the text Toula cited figures 1 and 2 of plate 25 for Capulus? gatsnensis. According to the explanation of the plate and the dimensions, leowever, figure 2 is his Capulus? sp. Figure 2 quite certainly represents a mold of the coarsely sculptured Crucibulmn that occurs in the Gatun formation. Perhaps through this error in citation Anderson was led to use the nanse Crucibulum gatunense for that species.
Occurrence: Lower, middle, and upper parts of Gatun formation (middle and late Miocene). Lower part, localities 137, 137a, 138, 138a, 139. Middle part, eastern area, localities 146, 147b, 147e, 147f (identifiration doubtful, immature specimens only), 147g,






GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


147h, 151, 152, 155, 155a, 155b, 155c, 159, 160 (Crucibulum cf. C. springvaleense); western area, locality 162a. Upper part, western area, locality 185. Springvale formation (late Miocene), Trinidad. Miocene, Bolivar, Colombia.
Family NATICIDAE
Subfamily NATICINAE
Genus Natica Scopoli
Scopoli, Introductio ad historiam naturalem, p. 392, 1777. Type (logotype, Harris, Catalogue of Tertiary Mollusca in the
British Museum; pt. 1, Australasian, p. 255, 1897); Nerita
vitellus Linn6, Recent, tropical western Pacific.
Anton (1839, p. 31) also designated Nerita vitellus as the type of Natica at a much earlier date than Harris. Anton's designation, however, is of doubtful validity, as it is a designation for Natica Lamarck.
Subgenus Natica s. s.?
Natica (Natica?) species
The collections from the marine member of the Bohio(?) formation at Vamos Vamos include two naticid opercula that have a narrow marginal rib, separated by a shallow groove from a wider second rib. They represent Aatica s. s. or possibly some other subgenus that has a similar operculum. The larger specimen has a restored length of about 12 millimeters and a width of 7.5 millimeters. Small poorly preserved shells from locality 42 may represent this species.
Occurrence: Marine member of Bohio(?) formation (late Eocene or early Oligocene), localities 40, 40d, 42 (identification doubtful).
Natica (Natica?) bolus Brown and Pilsbry Plate 20, figures 1-3
Natica bolus Brown and Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 64, p. 508, pl. 22, fig. 9, 1913 (Miocene, Canal Zone). Natica young Maury, Bull. Am. Paleontology, v. 5, no. 29, p. 135, pl. 23, figs. 11, 12, 1917 (Miocene, Dominican Republic). Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 73, p. 386, pl. 34, fig. 21, 1922 (Miocene, Dominican Republic). Maury, Bull. Am. Paleontology, v. 10, no. 42, p. 239, pl. 40, fig. 4, 1925 (Miocene, Trinidad). Mansfield, U. S. Natl. Mus. Proc., v. 66, art. 22, p. 57, 1925 (Miocene, Trinidad). Natica finitima Pilsbry and Johnson, Acad. Nat. Sci. Phila. Proc., v. 69, p. 173, 1917 (Miocene, Dominican Republic). Not Natica youngi Maury, Li, Geol. Soc. China Bull., v. 3, p. 266, pl. 6, figs. 47, 47a, 1930 (Miocene, Panama Bay; Natica unifasciata Lamarck, fide Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 83, p. 432, 1931, Recent, PanamA Bay). Not Natica (Polinices) cf. youngi Maury, Trechmann, Geol. Mag., v. 72, p. 550, pl. 20, figs. 3-5, 1935 (Miocene, Carriacou); Polinices sp.
Of medium size, thick-shelled, spire very low or moderately low, shoulder strongly or slightly inflated. Protoconch not clearly differentiated from remainder of shell, apical whorl large. Umbilicus wide, umbilical rib


narrow, ending in a small callus lobe bearing a shallow anterior depression. A narrow deep groove lies in front' of umbilical rib and callus pad, separating them froui umbilical border. Parietal callus thick, especially in front of junction with outer lip, where it forms a ridge. On immature shells anterior part of parietal callus relatively wider than on mature shells and roofing over posterior end of umbilicus as it extends forward to join-' umbilical lobe. Operculum assumed to represent this species bearing a narrow marginal rib, separated by a narrow groove from a second rib that is as narrow as the marginal rib or slightly wider.
Height 14.5 mm, diameter 15.2 mm (figured mature specimen). Height 9.7 mm, diameter 10.2 mm (figured immature specimen).
Type: Acad. Nat. Sci. Phila. 3846.
Type locality: Gatun Locks excavation, Canal Zone, middle part of Gatun formation.
The type, the largest of 6 in the type lot, is a small immature shell (height 9 millimeters). On the type and~ other immature shells, such as that shown on plate 20, figure 3, the anterior part of the parietal callus is wide and roofs over the posterior end of the umbilicus. On mature shells more of the umbilicus is uncovered. The. largest shell, which is incomplete, has a height of 19.5 millimeters. Very low-spired shells have an inflated shoulder, whereas shells that Pave a higher spire have a less inflated shoulder. Two small opercula assumed to represent N. bolus were found in association with shells at locality 155c and another of medium size at locality 172.
Though Natica bolus is fairly widespread in the Gatun formation, only a few specimens were collected at any, locality, except locality 177b. N. youngi, from the Miocene of the Dominican Republic, reaches a somewhat larger size (height 24 millimeters), but has the umbilical and callus features, as well as the outline, of N. bolus. N. youngi from the Miocene of Trinidad has a narrower umbilicus and less conspicuous umbilical rib than N. bolus, but is considered conspecific. N. young cocleana Olsson (1922, p. 155, pl. 13, fig. 8; Miocene,, Costa Rica), however, has a narrow umbilicus, weak umbilical rib, and narrower umbilical callus lobe, and evidently is not closely related. An early Miocene species from Costa Rica, N. milleri Gabb (1881, p. 338, pl. 44, fig. 3) has a higher spire and weaker umbilical rib. N. castrenoides Woodring (1928, p. 377, pl. 30, fig. 5;1 Miocene, Jamaica) and its Recent Caribbean analog,i N. castrensis Dall (1889, p. 293), have a wider and weaker umbilical rib and thinner parietal callus. N.J bolus appears to have no close living allies in either, Caribbean or Panamic waters.
The strong, though narrow, umbilical rib indicates that N. bolus is not closely related to N. vitellus; it


84







GASTROPODS: TROCHIDAE TO TURRITELLIDAE


probably is to be assigned to an unnamed subgenus. As pointed out by Powell (1933, p. 165), undue emphasis on operceular characters in effecting a classification of naticids may lead to artificial alliances.
Occurrence: Lower, middle, and upper parts of Gatun formation (middle Miocene). Lower part, locality 138. Middle part, eastern area, localities 142, 144 (incomplete, identification doubtful), 147b, 147g, 155, 155a, 155b, 155c, 157, 159; western area, localities 161a, 161c, 161d. Upper part, eastern area, localities 172, 173, 175, 176a, 177, 177a (incomplete, identification doubtful), '177b, 178. Cercado and Gurabo formations (middle Miocene), Dominican Republic. Springvale formation (late Miocene), Trinidad.
Subgenus Naticarius Dum6ril
Dum6ril, Zoologie analytique, p. 164, 1806; genus without species. Type (monotype, Froriep, C. Dumtril's analytische Zoologie, p.
165, 1806; quoted from Iredale, Malacol. Soc. London Proc., v. 12, p. 83, 1916): Nerita canrena Linns, Recent, West Indies.
The status of Dumlril's names, all of which end in "arius", will not be settled without a specific ruling, for they may be interpreted in various ways. According to Opinion 148 of the International Commission on Zoological Nomenclature, issued in 1943 A generic name published as an emendation of an earlier name of the same origin and meaning is to be rejected as a synonym of the earlier name, and the type of the genus bearing the emended name is automatically the same species as the type of the genus bearing the earlier name so proposed to be emended. Dumeril's names doubtless are emendations of earlier names of the same origin and meaning. All of them can be matched with earlier names that lack the "arius" termination. He probably emended the earlier names with the Latin suffix "arius" (pertaining to) as the name of the animal; Naticarius, for example, being the name of the animal "pertaining to" the shell Natica. His statement that "notre objet 6toit de faire connoltre les animaux et non les couquilles que les revltent" supports that interpretation. In that eves-t it could be argued that the names are to be rejected on the grounds that Dumlril adopted a system that results in two names for shell-bearing mollusks. If the nasmes are to be accepted and are emendations, and therefore synonyms, is Naticarius a synonym of Natica Scopoli or of Natica Lamarck? If it is a synonym of Natica Lamarck, it is available in place of that name, which is a homoncym of Natica Scopoli. Dumesril's names, however, were not admitted to be emendations when they were proposed. They therefore may be interpreted as entirely new names dating from his or Froriep's usage, depending on whether Dumiril's usage is considered nude. For the time being the view that they are new names is arbitrarily adopted. In 1928 Naticarius was regarded as a substitute name for Natica Lamarck not Scopoli


(Woodring, 1928, p. 378). That view, which followed Iredale's (1916, p. 82) interpretation, is far fetched, but has the same nomenclatorial effect as the view adopted in the present report.
Natica s s., or naticids having similar opercula, occur in the Eocene (Harris and Palmer, 1946-47, p. 247, pl. 29, figs. 1, 2, 1947; Wrigley, 1949, p. 11, 13, figs. 1, 2, 8-12). Naticarius, however, evidently does not antedate the late Oligocene. The late Eocene (Jackson) Natica permunda Conrad, which has been referred to Naticarius (Harris and Palmer, 1946-47, p. 246, 1947), lacks the axial grooves of that subgenus, and has a less rapidly enlarging umbilical rib and correspondingly narrower umbilical callus lobe. Naticarius is now found in western Atlantic and eastern Pacific tropical and subtropical waters. The Mediterranean N. millepunctata Lamarck has a multiribbed operculum, suggesting alliance with Naticarios, but the ribs are very narrow and the shell has a narrow usmbilical rib. This species has been erroneously assigned to Nacca Risso. An unidentified species of Naticarius occurs in tseupper part of the Bohio formation and poorly preserved fossils from the middle member of the Caimito formation in the Gatun Lake area and the Culebra formation are identified as Natica (Naticarius?) sp. They have a relatively high spire and short axial grooves adjoining the suture. Their umbilical features and opercula are unknown.
Natica (Naticarius) stenopa Woodring, n. sp.
Plate 20, figures 4-6
Of lledium size, thin shelled, moderately inflated, whorls enlarging at moderate rate, spire high. Protoconch of 2)) to 3 whorls, apical whorl small. End of protoconch marked by slight change in texture of shell and beginning of sculpture. Sculpture consisting of short closely spaced retractive axial grooves, parallel to growth lines, extending from suture and ending on shoulder on later whorls. Umbilicus moderately wide, umsobilical rib rapidly enlarging, ending in a wide callus lobe, the anterior part of which is concave. A very narrow deep groove in front of umbilical rib and ucbilical callus lobe. Parietal callus smloderately thick. Opercului bearing a marginal rib and 4 or 5 wider flat ribs, all separated by deep grooves.
Heig t 15.2 mm, diameter 14.8 mmsc (type). Height 21.5 ms, diameter 19.5 mml111 (largest specimen).
Type: US'NM 561340; paratype, USNM 561341; paratypes Stanford Unv.
Type locality: 177b (USGS 5854, Mouct Hope, west side of Panama Railroad near oil tanks, Canal Zone), upper part of Gatun foruatioc.
Natica stenopa is widespread and locally common in the Gatun formation, especially abundant in te upper


85







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


part of the formation in the eastern area. Eighteen of the 21 lots, however, consist only of immature specimens, up to a maximum of 115 immature shells in one lot. The largest shells are imperfect. A shell of medium size from locality 177c has an operculum in place (pl. 20, fig. 6). An incomplete operculum of medium size, not associated with shells, was found at locality 161. A small incomplete operculum, collected at locality 162, has three ribs, an indeterminate number of other lower ribs being covered with a glaze of enamel. The identification of this operculum is uncertain. The axial grooves disappear on the body whorl of an incomplete doubtfully identified shell from locality 147h.
Though Brown and Pilsbry (1913, p. 508) recorded N. canrena from the Gatun formation and though Olsson (1922, p. 155, pl. 13, fig. 9) figured a specimen of that Recent Caribbean species from the Gatun formation near Gatun, that species is not represented in the Gatun collections of the U. S. National Museum or Stanford University. N. stenopa is of meduim size and has a high spire, small apical whorl, closely spaced axial grooves, and 5 or 6 ribs on the operculum. N. canrena, on the contrary, is much larger and has more inflated and more rapidly enlarging whorls, low spire, large apical whorl, more widely spaced axial grooves, more rapidly enlarging umbilical rib and correspondingly larger umbilical callus lobe, and 8 or 9 ribs on the operculum.
On the basis of shell characters N. stenopa is closely related to a Recent Panamic species identified by Dall as N. limacina Jousseaume (1874, p. 14, pl. 2, figs. 7, 8). Jousseaume's description and illustrations suggest that the identification is erroneous. The operculum of N. limacina is unknown and the type locality is indefinite: "West Indies(?)". Dall's N. limacina is represented in the collections of the U. S. National Museum by one shell dredged in PanamS Bay at a depth of 33 fathoms. N. stenopa has a somewhat thinner shell, narrower groove in front of the umbilical rib and umbilical callus lobe, and wider umbilical opening back of the umbilical rib. Naticarius opercula, having 7 to 9 ribs, are represented by 2 lots from Panamai Bay, and also by lots dredged in the Gulf of California off Guaymas and La Paz, but it is not known that the opercula are to be associated with Dall's N. limacina. They agree with the operculum of N. colima Strong and Hertlein (1937, p. 174, pl. 35, figs. 12, 13, 16), dredged near Manzanillo, Mexico. N. colima, however, is thin shelled and has a very narrow umbilical rib and small umbilical callus lobe.
Natica canrena or allied forms are widespread in the Caribbean region in formations of Miocene and Pliocene


age. N. precanrena F. Hodson (Hodson, Hodson, and Harris, 1927, p. 68, pl. 36, figs. 2, 6, 9), a small Venezuelan early Miocene species (height 6.8 millimeters), has a high spire, small initial whorl, and closely spaced axial grooves. It has, however, a higher spire and a wider umbilicus than small specimens of N. stenopa.
Occurrence: Lower, middle, and upper parts of Gatun formation (middle and late Miocene). Lower' part, localities 136, 137, 137a, 138, 138a. Middle part, eastern area, localities 146, 147b, 147g, 147h (incomplete, identification doubtful), 151, 155, 155c, 157; western area, localities 161, 161a, 161c, 161d, 170, 170a. Upper part, eastern area, localities 175, 176a, 177b, 177c; western area, localities 183, 185.
Genus Stigmaulax Mdrch
M6rch, Catalogus conchyliorium Comes de Yoldi, pt. 1, p.
133, 1852.
Type (logotype, Harris, Catalogue of Tertiary Mollusca in the
British Museum; pt. 1, Australasian, p. 262, 1897): Natica
sulcata Born (Nerita sulcata Born), Recent, West Indies.
Stigmaflax, like Naticarius, lives in American tropical and subtropical waters on both sides of Central America. It is found in the late Tertiary of the same region, the earliest species being of early Miocene age.
Stigmaulax guppiana (Toula)
Plate 20, figures 11-16
Natica guppiana Toula, K. k. Geol. Reichsanstalt Jahrb., Band
58, p. 696, pl. 25, fig. 6, 1909 (Miocene, Canal Zone). Hodson, Hodson, and Harris, Bull. Am. Paleontology, v. 13, no. 49,
p. 67, pl. 36, figs. 1, 4, 1927 (Miocene, Venezuela).
Nlatica guppyana Toula, Engerrand and Urbina, Soc. Geol.
Mexicana Bol., v. 6, p. 130, pl. 60, figs .53, 54, 55 (reproduction of Toula's illustration), 1910 (Miocene, Mexico). Brown and Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 63, p. 360, 1911 (Miocene, Canal Zone). Olsson, Bull. Am. Paleontology, v. 9, no. 39, p. 156, pl. 13, figs. 13-15, 1922 (Miocene, Panamd, Costa Rica). Anderson, California Acad. Sci. Proc., 4th ser., v. 18, no. 4, p. 123, 1929 (Miocene, Colombia). Tucker and Wilson, Bull. Am. Paleontology, v. 18, no. 65, p. 13, pl. 2, figs. 3, 4, 1932 (Miocene, Florida). Mansfield, Florida Dept.
Conservation, Geol. Bull. 12, p. 10, 13 (lists), 1935 (Miocene,
Florida).
Natica (Stigmaulax) sulcata guppiana Toula, Rutsch, Schweizer.
Palacont. Gessel. Abh., Band 54, no. 3, p. 51, pl. 1, fig. 15 (type),
1934 (Miocene, Canal Zone).
Natica (Naticarius) guppyana Toula, Oinomikado, Geol. Soc.
Japan Jour., v. 46, p. 621, pl. 29, fig. 18, 1939 (Miocene,
Colombia).
Natica (Stigmnaulax) guppiana Toula, Gardiner, U. S. Geol. Survey Prof. Paper 142, p. 546, pl. 59, fig. 9 (reproduction of Toula's illustration), 1947 (Miocene, Florida). Natica (Stigmaulax) guppiana toulana Gardner, idem, p. 547, pl. 59, figs. 7, 8, 1947 (Miocene, Florida). Natica (Stigmaulax) guppyana Toula, Marks, Bull. Am. Paleontology, v. 33, no. 139, p. 98, 1951 (Miocene, Ecuador). Operculum (sp.?), Toula, K. k. Geol. Reichsanstalt Jahrb., Band 61, P. 511, p1. 31. fCo. 26. 1911 (Miocene. Canal Zone).


86






GASTROPODS: TROCHIDAE TO TURRITELLIDAE


Not Natica guppyana Toula, Li, Geol. Soc. China Bull., v. 3, p. 266, pl. 6, fig. 46, 1930 (Miocene, Panama Bay; =Natica elenae 6cluz, fide Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 83, p. 432, 1931, Recent, Panama Bay). Large, thick shelled, spire low, whorls strongly inflated and rapidly enlarging. Protoconch of 2% to 2y whorls, apical whorl small. Sculpture of relatively widely spaced retractive axial grooves, parallel to growth lines, extending away from suture and generally ending at or above periphery. On some shells they extend to umbilical region, but not on last half of body whorl of large shells. Umbilicus very wide, umbilical rib rapidly enlarging, ending in a moderately wide callus lobe, the anterior part of which is concave on large shells and strongly excavated on shells of small and medium size. On shells of large and medium size a more or less distinct supplementary rib lies on umbilical rib at its posterior border and may modify outline of callus lobe. Groove in front of umbilical rib and umbilical callus lobe moderately wide on large shells, narrow on others. Parietal callus very thick. Operculum dominated by very wide thick warty central rib. Marginal rib very narrow, denticulate. Several minor ribs, two of which generally are undercut along their inner margin, lie between marginal and central ribs. Outermost minor rib irregularly roughened.
Height 33.5 mm, diameter 30.5 mm (figured large specimen with short axial grooves). Height 30.5 mm, diameter 29 mm (figured large specimen with axial grooves extending from suture to umbilical region on first half of body whorl).
Type: Tech. Hochschule, Vienna (temporarily at Geol. Inst., Univ. of Berne, Switzerland).
Type locality: Presumably Gatun Locks excavation, Canal Zone, middle part of Gatun formation.
Stigmaflax guppiana is the most widespread and most abundant of the Gatun naticids and was found in the Chageas sandstone at the mouth of Rio Indio. All of the numerous large shells and many of medium size have one or more healed breaks on the body whorl. The more widely spaced axial grooves and the excavated umbilical callus lobe differentiate very young shells from very young shells of Natica stenopa. The sculpture is variable. Shells of large and medium size on which the axial grooves extend to the umbilical region are common only in the ipper part of the Gatun formation in the eastern area. Locality 155c is the only locality in the middle part of that formation where all the specimens collected have grooves extending to the umbilical region. No large shell has grooves extending to the umbilical region on the later half of the body whorl. Though the body whorl of some large shells shows indistinct microscopic spiral lineation, like that on some specimens of Natica canrena, there is no gross


87


spiral sculpture. The supplementary umbilical rib is of variable strength, but is visible on shells of large and medium size.
Opercula are not rare. They were collected at 11 localities, as many as 10 at a locality. A large shell having the operculum in place (pl. 20, fig. 18) was collected by T. F. Thompson. The only other in place is in a minute shell, which has a height of 1.5 millimeters (locality 147b). Details of opercular sculpture are variable, especially the number of minor ribs. The fine denticles on the very narrow marginal rib are obscure on some large opercula. That the thick callus of the warty central rib conceals flat minor ribs, like those adjoining the central rib on some opercula, is shown by the mergence of such ribs on 2 large opercula, (pl. 20, figs. 13, 18). Toula described a small operculum without realizing that it belongs to a species he had named.
Forms of Stigmaulax closely related to the Recent Caribbean S. sulcata (Born) are found in Miocene formations in Jamaica, Haiti, the Dominican Republic, Puerto Rico, and Brazil. S. guppiana, however, is not one of them. It lacks gross spiral sculpture and is snore closely allied to the Recent Panamic S. broderipiana (Recluz), as pointed out by Olsson (1932, p. 207). S. broderipiana is smaller and has a less depressed suture. The opercula of the two species are similar, but the central rib of S. broderipiana has a narrow crest. S. elenae (RScluz), also a Recent Panamic species, is another close ally. It also has a less depressed suture and its axial grooves are in general more closely spaced. The single available operculum has a narrower central rib. The color pattern, however, is the most distinctive feature of S. elenae.
S. goppiana is found in the Gurabo formation of the Dominican Republic. A close ally of S. sulcata also occurs in the Gurabo formation, but not at the same localities. This close ally of S. sulcata was recorded as S. vererugosum (Cossmann) (Woodring, 1928, p. 383) and has been named Natica sulcata gurabensis by Rutsch (1934, p. 52, pl. 2, fig. 10). S. guppiana also occurs in deposits of middle and late Miocene age in Florida. The collection from Shell Bluff on Shoal River (USGS 3742) consists of numerous specimens, all smaller than large shells from the Canal Zone. The collection also includes 3 opercula which agree with opercula of S. guppiana. Two specimens from locality 3742 that have short axial grooves were named Natica guppiana toulana by Gardner. This is the common form in the lower and middle parts of the Gatun formation, and the numerous Gatun collections show gradation in the length of the grooves. The single specimen (height 22 millimeters) from Vaughan Creek (USGS 12046) agrees closely with Gatun shells




l


GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


88


of medium size that have grooves extending to the umbilical region. According to Tucker and Wilson, S. guppiana occurs in upper Miocene deposits at Acline, Florida.
A large Stigneelax from the late Miocene Punta Gavilln formation of Venezuela has been described as Natica (Stigmaulax) sulcata beaumonti Rutsch (1934, p. 50, pl. 2, figs. 6-8, pl. 3, fig. 5). I am indebted to Dr. Rutsch for two topotypes of this form. It is allied to S. guppiana and may be considered a subspecies of S. guppiana. It is considerably larger than S. guppiana proper (height 42 millimeters), but even on these large shells the axial grooves continue to the umbilical region almost to the outer lip. This large form, S. guppiana beaumonti, and the typical form of S. guppiana in the Chagres sandstone are the last Caribbean allies of S. broderipiana.
Occurrence: Lower, middle, and upper parts of Gatun formation (middle and late Miocene). Lower part localities 137, 137a, 138, 138a. Middle part, eastern area, localities 142, 146, 147 (identification doubtful), 147b, 147f, 147g, 147h, 150a, 151, 153, 153a, 1551, 155b, 155c, 156, 157, 158 (identification doubtful); western area, localities 161, 161c, 161d. Upper part, eastern area, localities 172, 175, 176, 176a, 177a, 177b, 177c, 178; western area, localities 182, 182a, 183, 185. Chagres sandstone (early Pliocene), locality 208. Miocene, Falc'n, Venezuela. Middle Miocene, Bolivar and Choc6, Colombia. Daule formation (middle Miocene), Ecuador. Middle Miocene, northeastern Panami and Costa Rica. Miocene, Chiapas, Mexico. Shoal River formation (middle Miocene), Florida. Late Miocene deposits at Acline, Florida.
Genus Tectonatica Sacco
Sacco, Mus. Zoologia Anatomia Comparata R. Univ. Torino Bel., v. 5, no. 86, p. 33, 1890.
Type (monotype): Tectonatica tectula Bors. (error for Bon.)
(Natica tectula Bonelli), Miocene and Pliocene, Italy.
Though the name Tectonatica has been used for small tropical American species (Woodring, 1928, p. 384), that usage was not entirely satisfactory, because no specimens of the type species were examined. Through the kindness of John Q. Burch, of Los Angeles, a specimen of Natica tectula identified by Sacco is now available. It is larger than the small tropical American species (height 7 millimeters; maximum height 12 millimeters, according to Sacco) and the umbilical callus lobe does not completely fill the umbilicus, leaving a narrow unfilled space, comparable to the narrower space of varying width on the small American "Natica" pusilla Say. In his later description of Tectonatica. Sacco (1891, p. 81) described the operculum as calcareous. He evidently was relying on allied Recent species, as in his description of Natica tectula the


operculum is not mentioned. Though the operculum of that species evidently is still unknown, there is no reasonable doubt that Tectonatica is an appropriate name for the small American species. The type of Cryptonatica (Dall, 1890-1903, p. 362, 1892; type (logotype, Dall, 1909, p. 85): Natica clause Broderip and Sowerby) is a large arctic and boreal species, on which the umbilical callus lobe completely fills the umbilicus. Like the small species, it has a smooth calcareous operculum. When the anatomy of the large arctic and small tropical species is known, both names (Tectonatica and Cryptonatica) may be found to be useful.
Tectonatica has been recognized in the Eocene of England (Wrigley, 1949, p. 14).

Tectonatica species
Two imperfect specimens record the occurrence of a small inflated species of Tectonatica in the late. Eocene or early Oligocene strata of Trinidad Island. The unbilical callus lobe is preserved on the smaller specimen, but is absent (presumably dissolved) on the larger. The larger specimen has a more strongly bulging body whorl than T. agna of the Gatun formation. T. foridana (Dall) (1890-1903, pt. 2, p. 366, pl. 17, fig. 5, 1892), of the early Miocene Tampa limestone of Florida, is more than three times as large and is more elongate. Heretofore T. foridana was the earliest recorded east American species.
The larger specimen has the following dimensions: height 2.4 mm, diameter 2.6 mm.
Occurrence: Marine member of Bohio(?) formation (late Eocene or early Oligocene), Gatun Lake area, locality 42.
Tectonatica agna Woodring, n. sp.
Plate 17, figure 46
Very small, strongly inflated, spire low or moderately low. Protoconch not clearly differentiated from remainder of shell, apical whorl small. Umbilical callus lobe thick, completely filling umbilicus, bearing a shallow central depression. Edge of umbilical callus lobe raised above level of umbilical border. Parietal callus thick. Operculum unknown.
Height 2.8 mm, diameter 2.4 nn (type).
Type: USNM 561348; paratypes, Stanford Univ.
Type locality: 147b (USGS 6033c, Panama Railroad, about 3,500 feet (1,065 meters) southeast of Gatun railroad station, Canal Zone), middle part of Gatun formation.
This minute Tectonatica, like many other small species from the Gatun formation, is abundant at locality 147b, the type locality. The shallow, but distinct, depression on the umbilical callus lobe is its







GASTROPODS: TROCHIDAE TO TURRITELLIDAE


most distinctive feature. On a few shells the suture on the last half of the body whorl descends more sharply than on the common form, producing a correspondingly higher spire.
The more distinct depression on the umbilical callus lobe and the narrower groove at the outer edge of the ,lobe differentiate Tectonatica agna from T. pusilla (Say), which moreover is slightly larger. T. pusilla is the only fossil Tectonatica recorded from the Caribbean region (Woodring, 1928, p. 384, pl. 30, fig. 12). It now ranges from Massachusetts to Florida. A Recent West Indian species, possibly T. sagraiana (d'Orbigny) also lacks the callus depression. No Recent Panamic species is represented in the U. S. National Museum collection.
Occurrence: Middle and upper parts of Gatun formation (middle and late Miocene). Middle part, eastern area, localities 146, 147b, 147f, 147g, 147h, 151, 153a. Upper part, eastern area, locality 177c; western area, locality 185 (identification doubtful).
Subfamily POLINICINAE
Genus Polinices Montfort
'Montfort, Conchyliologie syst6matique, v. 2, 1. 223, 1810. Type (orthotype): Polinices albus Montfort (==Natica mamnilaris
Lamarck=Natica brunnea Link), Recent, West Indies.
Incomplete and poorly preserved naticids from the Gatuncillo formation, the marine member of the Bohio(?) formation, and the Culebra formation are doubtfully referred to Polinices. The umbilical features of these fossils, most of which are molds, are not known.

Polinices canalizonalis (Brown and Pilsbry) Plate 20, figures 7, 8
Natica canalizonalis Brown and Pilsbry, Acad. Nat. Sci. Phila.
Proc., v. 64, p. 508, pl. 22, fig. 10, 1913 (Miocene, Canal Zone).
Of medium size, thick-shelled. Body whorl appressed at suture, strongly inflated below appressed area. Aperture small for size of shell. Apical whorl small. Faint microscopic spiral lineation visible on unworn parts of shell. Umbilicus wide. Umbilical rib strong on immature shells, somewhat flattened on mature shells, ending in a wide callus lobe. Parietal callus very thick, bearing a shallow transverse groove.
Height 21 mm, diameter 18.7 mm (figured mature specimen). Height 11 mm, diameter 10 mm (figured immature specimen).
Type: Acad. Nat. Sci. Phila. 3844.
Type locality: Gatun Locks excavation, Canal Zone, middle part of Gatun formation.
Polinices canalizonalis is the least abundant of the three Gatun species of Polinices. It also is the only one of the three that has a conspicuous umbilical rib.


The type is an immature shell (height 8.2 millimeters). The well-defined umbilical rib indicates alliance with a Recent Caribbean species labelled P. porcellanus (d'Orbigny) in the U. S. National Museum collection. The Recent species has a stronger rib and is less appressed at the suture. P. carolinianus (Conrad) (Mansfield, 1930, p. 127, pl. 19, fig. 1), which occurs in the Duplin formation of North Carolina and in deposits of late Miocene age in western Florida, is larger, less appressed at the suture, and has a stronger rib. A late Miocene species from Trinidad, P. boutakoffi Rutsch (1942, p. 139, pl. 6, figs. 7a, 7b), belottgs in this group of species characterized by a strong umbilical rib. According to Rutsch's illustrations, it is more inflated, less appressed at the suture, and has a deeper groove on the parietal callus.
Occurrence: Lower middle, and upper parts of Gatun formation (middle Miocene). Lower part, locality 136a. Middle part, eastern area, Gatun Locks excavation (Brown and Pilsbry); western area, locality 161a. Upper part, eastern area, localities 177b, 177c.

Polinices brunneus subclausus (Sowerby) Plate 20, figure 9
Natica subclausa Soeicrby, Geol. Soc. London Quart. Jour., v. 6,
p. 51, 1850 (Miocene, Doniticea Republic).
Polinices subclausa (Sowerby), Brown and Pilsbry, Acead. Nat.
Sci. Phila. Proc., v. 63, p. 360, 1911 (Miocene, Canal Zone).
Maury, Bull. Am. Paleontology, v. 5, no. 29. p. 136, pl. 23, fig. 14, 1917 (Miocene, Dominican Republic). Olsson, idem, v. 9, no. 39, p. 157, pl. 13, figs. 16-17, 1922 (Miocene, Costa Rica, Canal Zone). Hodson, Hodson, and Harris, idem, v. 13, no. 49, p. 69, pl. 36, fig. 5, 1927 (Miocene, Jamaica).
Anderson, Calif. Acad. Sci. Proc., 4th ser., v. 18, no. 4, p. 124,
1929 (Miocene, Colombia, Canal Zone).
Polinices srunnea subclausa (Sowerby), Woodring, Carnegie Inst.
Washington Pub. 385, p. 385, pl. 30, fig. 13, 1928 (Miocene,
Jamaica); see this publication for other citations.
?Polinices (Mammilla) cf. brunnea Link, Weisbord, Bull. Am.
Paleontology, v. 14, no. 54, p. 29, pl. 9, fig. 12, 1929 (Miocene,
Colombia).
Of meditu size, thick shelled. Whorls strongly and smoothly appressed at suture. Apical whorl small. Umbilicus ttsoderately narrow; tmbilical rib almost flat. Umbilical callus lobe narrow, slightly widened by umbilical rib. Parietal callus very thick, bearing a shallow transverse groove.
Height 20.3 tote, diameter 16.7 tm (figured specite en).
Type material: British Mus., Natural History, Geol. Depart., Geol. Soc. London 12826 (6 syntypes).
Type locality: Dominican Republic, Miocene.
This Polinices is fairly cotmton in the middle part of the Gatun formation at locality 161c, west of Gatun Dam, and occurs at other localities, all in the middle part of the Gatun formation. The groove on the


89







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


parietal callus is relatively deep on some small speci-. mens. The largest Gatun shells are half as large as the largest from the Miocene of the Dominican Republic and Bowden, Jamaica (height 40 millimeters), and are much smaller than large specimens of the Recent Caribbean P. brunneus proper (height 50 millimeters). Like the Miocene fossils from the Dominican Republic and Jamaica, the Gatun fossils have a slightly narrower umbilicus than Recent shells of the same size. The fairly wide umbilicus of Weisbord's Polinices cf. P. brunnea indicates,however,that the Miocene form cannot consistently be distinguished by the width of the umbilicus. Recent shells that are not worn show a faint microscopic spiral lineation, which has not been observed on the fossils from the Canal Zone, the Dominican Republic, and Jamaica. The apparent absence of lineation on the fossils, however, may be due to slight wear. A small form of P. brunneus subclausus from the Miocene of Banana River, Costa Rica, has faint spiral lineation and also has a deep groove on the parietal callus, as shown by Olsson's illustrations.
A form of P. brunneus subclausus that has a notch between the parietal callus and the umbilical callus lobe has been recognized in the Miocene of Venezuela and Jamaica, and has been named P. subclausa lavelana F. Hodson (Hodson, Hodson, and Harris, 1927, p. 69, pl. 36, fig. 8, pl. 37, figs. 12, 14).
Polinices nelsoni Olsson (1932, p. 208, pl. 24, figs. 8, 10), which is more slender than P. brunneus and has a narrower ambilicus, is a late Miocene Peruvian relative of P. brunneus, but no close allies are known to be living in the Panamic region.
Occurrence: Middle part of Gatun formation (middle Miocene), eastern area, localities 155b, 155c; western area, localities 161 (immature, identification doubtful), 161c, 161d, 170 (immature, identification doubtful). Cercado and Gurabo formations (middle Miocene), Dominican Republic. Bowden formation (middle Miocene), Jamaica. Middle Miocene, Costa Rica. Miocene, Bolivar, Colombia.
Polinices stanislas-meunieri Maury
Plate 21, figures 11-14
Polinices stanislas-meanieri Maury, Bull. Am. Paleontology,
v. 5, no. 29, p. 136, pl. 23, figs. 15-16, 1917 (Miocene, Dominican Republic). olsson, idem, v. 9, no. 39, p. 157, pl. 13, fig. 7, 1922 (Miocene, Costa Rica). Maury, idem, v. 10, no. 42, p. 240, pl. 40, fig. 7, 1925 (Miocene, Trinidad). Anderson, Gallf. Acad. SCl. Proc. 4th ser., v. 18, no. 4, p. 124, 1929 (Mioceae, Columbia).
Polinices stanislas-meunieri venezuelana F. Hodson, Bull. Am. Paleontology, v. 13, no. 49, p. 70, pl. 37, figs. 10, 15, 1927 (Miocene, Venezuela).
Not Polinices stanislas-mncunieri Maury, Li, Geol. Soc. China Bull., v. 9, p. 267, pl. 6, fig. 48, 1930 (Miocene, Panama Bay; =P. uber (Valenciennes) and P. rapulum limit Pilsbry, fide


Pilsbry, Acad. Nat. Sci. Phila. Proc., v. 83, p. 432, 1931,
Recent, Panama Bay).
Polinices springvalensis Maury, Bull. Am. Paleontology, v. 10,
no. 42, p. 241, pl. 40, fig. 6, 1925 (Miocene, Trinidad).
Moderately large, moderately thick-shelled, moderately slender to strongly inflated. Whorls not appressed at suture, except near outer lip or on most of body whorl of large specimens. Apical whorl small. Microscopic spiral lineation distinct on unworn shells. Umbilicus and umbilical callus lobe narrow. Parietal callus moderately thick, much wider than umbilical lobe, bearing a faint to distinct transverse groove on immature shells.
Height 43.5 mm, diameter 33 mm (figured large slender specimen). Height 32.5 mm., diameter 28 mm (figured inflated specimen).
Type: Cornell University 36931.
Type locality: Rio Cana, Dominican Republic, Gurabo (?) formation (middle Miocene).
Polinices stanislas-meunieri is the most widespread of the Gatun species of Polinices. It is locally common in the lower part of the formation, but many of the specimens are relatively slender, like that shown on plate 21, figure 14. The large figured specimen (pl. 21, fig. 13) was collected by T. F. Thompson. The umbiical rib is so flat that it is virtually absent. Therefore the narrow umbiical callus lobe widens very slightly. The umbiicus is of varying width on immature shells, and is practically closed on one from locality 136 (height 6 millimeters). The transverse groove on the parietal callus is absent on shells of large and medium size, and generally is faint on small shells.
Differentiation of P. stanislas-meunieri venezuelanus appears to be unwarranted. P. springvalensis is a shouldered form of P. stanislas-meunieri, but is not much more strongly shouldered than the Gatun specimen shown on plate 21, fig. 12. The early Miocene Costa Rican P. eminuloides (Gabb) (1881, p. 339, pl. 44, fig. 4) probably is related to P. stanislas-meunieri. The type, and only specimen, is high spired; the umbilical area is not completely exposed; and the parietal callus is damaged.
P. stanislas-meunieri is widely distributed in the Miocene of the Caribbean region, but has no living. allies there. It is closely related, however, to the Recent Panamic P. uber (Valenciennes). P. stanislasmesnieri is not much more than half as large, but its parietal callus is thicker than that of specimens of P. uber of the same size, indicating maturity. The outline of P. stanislas-meunieri ranges from strongly and smoothly inflated to moderately slender, whereas that of P. uber is more uniformly strongly and smoothly inflated.


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GASTROPODS: TROCHIDAE TO TURRITELLIDAE


P. coensis (Dall) (Mansfield, 1930, p. 124, pl. 17, fig. 8), which occurs in deposits of late Miocene age in western Florida, and P. robustus Gardner (1926-47, p. 550, pl. 59, figs. 5, 14, 1947), a middle Miocene form, are the representatives of P. stanislas-meanieri in the Miocene of Florida. P. coensis is smaller than the Caribbean ,species. It has a more distinct notch between the umbilical callus lobe and parietal callus, thicker parietal callus, and the transverse groove on the parietal callus persists to a later stage than on Gatun fossils. P. robustus, which perhaps is to be considered a large highspired subspecies of P. coensis, closely resembles highspired Gatun shells, but has a thicker parietal callus.
P. coensis is the type of the subgenus Dallitesta Mansfield (1930, pp. 124, 125), which was proposed without any discussion of differentiating characters. Perhaps it was proposed because of the distinct spiral lineation. Should the genus Polinices be subdivided into subgenera, Dallitesta would be available for species that have a narrow umbilicus, virtually no umbilical rib, narrow umbilical callus lobe, and distinct spiral lineation. There are, however, gradations from a strong umbilical rib, like that P. canalizonalis, to virtually none; and many species, including P. brunneus, the type of the genus, have more or less distinct spiral lineation.
Occurrence: Lower, middle, and upper parts of Gatun formation (middle and late Miocene). Lower part, localities 136, 136a, 137, 138, 138a. Middle part, eastern area, localities 140, 146 (immature, identification doubtful), 147b (immature, identification doubtful), 147g (immature, identification doubtful), 147h (immature, identification doubtful), 155, 155c (incomplete, immature, identification doubtful), 157, 159a; western area, localities 161, 161c. Upper part, eastern area, localities 171, 173 (incomplete, identification doubtful), 177b; western area, localities 182, 182a, 183, 185 (im,nature, identification doubtful). Middle Miocene, Cost. Rica. Gurabo(?) formation (middle Miocene), Dominican Republic. Miocene, Bolivar, Colombia. Miocene, Falc6n, Venezuela. Springvale formation (late Miocene), Trinidad.
Genus Neverita Risso
Risso, Histoire naturelle des principales productions de l'Europe
m6ridionale, v. 4, p. 149, 1826.
Type (monotype): Neverita josephinia Risso, Recent, Mediterranean Sea.
The Gatuncillo and Culebra formations, Emperador limestone member of the Culebra formation, and the La Boca marine member of the Panama' formation yielded molds of low-spired naticids identified as Neverita? sp. A large low-spired naticid from the marine member of the Bohio(?) formation near Palenquilla Point (diameter 39 millimeters), the umbilicus of which is not exposed, also is identified as Neverita? sp.


91


Subgenus Glossaulax Pilsbry
Pilsbry, Nautilus, v. 42, p. 113, 1929. Type (orthotype): Neverita reclusiana (Deshayes) (Natica
reclusiana Deshayes), Recent, southern California to Gulf of
California.
The subgenus Glossaulax embraces neverites that have a groove on the umbilical callus, dividing it into anterior and posterior lobes. The groove of the type species is located on the anterior part of the callus.
Glossalax is widely distributed on both sides of the northern Pacific and is represented in the Eocene of western North America by a typical species, N. seca Gabb, which Stewart (1927, p. 325) suggested may be treated better as a subspecies of N. reclusiana. This subgenus formerly had a more extensive distribution. It is represented in the Eocene of southeastern United States by N. limula (Conrad) (Palmer, 1937, p. 125, pl. 13, figs. 13, 14, 16, 19-22, pl. 80, figs. 13, 16), in the Eocene of the Caribbean region by N. bolivarensis Clark, and in the Eocene or Oligocene of Peru by N. subreclusiana (Olsson). These early Tertiary species are hardly typical, as the umbilical callus groove is not consistently present. Typical species, however, mentioned under N. reclusiana xena, are found in the Miocene of Florida and the Caribbean region.
Neverita (Glossaulax) bolivarensis tapina Woodring, n. subsp.
Plate 15, figures 7, 8, 11
Of medium size, depressed, conical. Umbilical callus partly filling umbilicus, the wide unfilled space decreasing in width toward parietal callus, but extending to junction of umbilical and parietal callus. Parietal callus set off from umbilical callus by a faint groove. Posterior part of umbilical callus bearing a faint groove. Umbilical wall faintly striate.
Height 14.5 mm, diameter 19 mm (type). Height 16.5 mm, diameter 26.5 mm (largest specimen).
Type: USNM 561354. Paratype, USNM 561442.
Type locality: 40d (USGS 6028a, Gatun Lake area, lower bed at Vamos Vamos, off Palenquilla Point, Canal Zone, now submerged), marine member of Bohio(?) formation.
Though Neverita bolivarensis tapina is represented by 12 specimens from the marine member of the Bohio(?) formation, only a few show the callus features. The callus is completely exposed on the type and paratype, both of which have a relatively wide unfilled umbilical space, a faint groove between the umbilical and parietal callus, and a faint groove on the posterior part of the umbilical callus. The groove on the umbilical callus of the type probably is modified by an artificial crack. The paratype has a shallow groove that disappears before reaching the umbihical border. Enough of the umbilical callus is exposed on two other specimens to







GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


show that a considerable part of the umbilicus is not filled.
This neverite is considered a subspecies of N. bolivarensis Clark (Clark and Durham, 1946, p. 16, pl. 15, figs. 10, 11, 14, 15, 18-20, 22, 26)-a subspecies characterized by its depressed outline and wide umbilical space gradually tapering toward the parietal callus. The specimen of N. bolivarensis proper shown by Clark on plate 15, figure 11, is depressed and has a wide umbilical space. The umbilical space, however, separates the callus from the entire umbilical wall. N. bolivarensis proper occurs in the late Eocene of Colombia. It and the subspecies from Panama are related to N. subreclusiana (Olsson) (1931, p. 68, pl. 10, figs. 1, 4), of the late Eocene or early Oligocene Chira shale of Peru'. That species has a high spire and practically filled umbilicus.
Occurrence: Marine member of Bohio(?) formation (late Eocene or early Oligocene), Gatun Lake area, localities 40, 40a, 40d, 41 (immature).
Neverita (Glossaulax) reclusiana xena Woodring, n. subsp.
Plate 21, figures 5, 8, 9
Of medium size, generally low spired. Spiral lineation visible on umlbilical wall, but not elsewhere, presumably due to slight wear. Posterior lobe of umbilical callus longer than anterior lobe, reaching umbilical wall. Space between umbilical wall and anterior lobe of umbilical callus narrow or very narrow.
Height 25 mm, diameter 27 mm (type). Height 34 mm, diameter (incomplete) 35 mm (figured large highspired specimen).
Type: USNM 561355; paratypes, Stanford Univ.
Type locality: 137 (USGS 16911, Transisthmian Highway, 1.7 kilometers northwest of Sabanita, PanamA), lower part of Gatun formation.
Neveriia reclusiana zena is based on 12 specimens from the lower part of the Gatun formation and one from the middle part. It is remarkably similar to a small form of N. reclusiana (Deshayes) found along the outer coast of Baja California and along the Gulf of California. The Gatun neverite in general has a narrower space between the umbilical wall and the anterior callus lobe. Some small Recent shells, however, are practically indistinguishable from the fossils. This Mexican form has been listed as a variety of N. reclisiana (Pilsbry and Lowe, 1932, p. 126), but its status is not yet satisfactorily determined.
Typical species of Glossaulax are found in the Miocene of Florida and the Caribbean region: N. chipolana (Dall) (Gardner, 1926-47, p. 551, pl. 59, fig. 22, 1947; Chipola formation, Florida), N. subporcana (F. Hodson) (Hodson, Hodson, and Harris, 1927, p. 70, pl. 36, fig. 3, pl. 37, figs. 5, 9, 16; Miocene, Venezuela), and N.


cuspidata (Guppy) (Maury, 1925, p. 239, pl. 40, figs, 9, 10; Rutsch, 1942, p. 140; Springvale formation, Trinidad). N. chipolana has a short anterior callus lobe; N. subporcana has a narrow anterior lobe and the posterior lobe leaves part of the umbilicus unfilled; N. cuspidata is very large (height 60 mm) and has short subequal lobes. There are no living species of Glossaulax in the Caribbean Sea or elsewhere in the western Atlantic. The late Miocene N. cuspidata is the last Caribbean species.
Inasmuch as N. reclusiana has a long history in the eastern Pacific going back to the Miocene, if not earlier, N. reclusiana xena evidently is a migrant from the Pacific. The present distribution of N. reclusiana and its allies, which are not found south of the Gulf of California, shows a marked reduction since Miocene time.
Occurrence: Lower and middle parts of Gatun formation (middle Miocene). Lower part, localities 136a, 137, 137a. Middle part, eastern area, locality 155.
Subgenus Hypterita Woodring, n. subgen.
Type: Natica helicoides Gray, Recent, Baja California to Perd.
Hypterita is proposed for neverites that are greatly depressed, and have a very wide umbilicus with gently sloping wall, a thin umbilical callus lobe perched on a narrow or moderately wide umbilical rib, and a very thin wash of parietal callus. This well defined group of neverites includes only two known species: the type species and the Miocene Caribbean Neverita nereidis. The type species is generally known as Neverita glauca (Lesson).
Neverita (Hypterita) helicoides (Gray)
Plate 18, figures 15, 16
Natica patula G. B. Sowerby, Zool. Jour., vol. 1, p. 60, pl. 5,
fig. 4, 1824 (Recent, locality unknown, but another specimen cited as South American). Barnes, Lyceum Natural History New York Annals, vol. 1, p. 136, 1824 (Recent, Perd). Not
Natica patula J. Sowerby, 1822.
Natica helicoides Gray, Zool. Jour., vol. 1, p. 511, footnote, 1825
(cited as manuscript name of Barnes).
Natica glauca "Humboldt", Lesson, Voyage autour du
monde * la Coquille *, Zoologie, vol. 2, pt. 1, p. 369, pl. 11, figs. 1, 1', 1830 (Recent, Perd). Naica bonplandi Valenciennes, in Humboldt and Bonpland,
Voyage aux rgions equinoxiales du nouveau continent, pt. 2, Recueil d'observations de zoologie, vol. 2, p. 264, pl. 57, figs. 3s, 3b, 1832 (Recent, Acapulco, Mexico; not seen). ?Neverita nereidis Maury, Olsson, Bull. Am. Paleontology, vol. 9, no. 39, p. 158, 1922 (Miocene, Costa Rica). Polinices (Neverita) glauca Humboldt, Olsson, idem, vol. 27, no.
106, p. 20 (list), 1942 (Pliocene, Costa Rica).
Polinices helicoides (Gray), Hertlei and Strong, Am. Mus.
Natural History Bull., vol. 107, art. 2, p. 287, 1955 (Recent, Baja California to Perd; see this publication for other citations).


92







GASTROPODS: TROCHIDAE TO TURRITELLIDAE


Of medium size. Microscopic spiral lineation of f,'sh Recent shells not apparent, presumably due to slight wear. Umbilical rib narrow, slowly enlarging; unfilled umbilical space wide.
Height (incomplete) 16 mm, diameter (incomplete) 34 mm (figured specimen).
The Gatun formation yielded three incomplete fossils that closely resemble Recent shells of Neverita helicoides "of medium size. The largest fossil, if it were complete, would have a diameter of about 45 millimeters. The largest Recent shells of N. helicoides in the U. S. National Museum collections have a diameter of between 55 and 60 millimeters. Slightly worn Recent shells do not show the very fine slightly wavy micro-scopic lineation of fresh shells.
Neverita nereidis Maury (1917, p. 137, pl. 23, figs. 17, 18), which occurs in the Cercado formation of the Dominican Republic, is closely allied to N. helicoides. Like the Gatun fossils, it is smaller than N. helicoides (diameter 35 mm). Moreover it has a wider umbilical rib than the Recent species. However remarkable it may be to recognize two very closely related species of Hypterita in the Miocene of the Caribbean region, the Gatun fossils are identified as N. helicoides on the basis of their narrow umbilical rib.
The fragment from the Miocene of Banana River, Costa Rica, identified by Olsson as N. nereidis, is not accessible at the present time. A fragment from that area, however, in the collections of the U. S. National Museum has a narrow umbilical rib and is doubtfully identified as N. helicoides.
Gray's name is far from satisfactory. He cited it as Barnes' manuscript name, a name that was still-born so far as Barnes' mention of it is concerned. Unfortunately the name, as Gray's name, is nomenclaturally available and therefore, as pointed out by Hertlein and Strong, replaces the well known name Neverita glauca.
Occurrence: Lower and middle parts of Gatun formation (middle Miocene). Lower part, locality 136a. Middle part, eastern area, locality 155b; western area, 'locality 161c. Middle Miocene, eastern Costa Rica (identification doubtful). Pliocene, western Costa Rica. Recent, Magdalena Bay, Baja California, and Gulf of
-California to Perd.
Subfamily SININAE
Genus Sinum Rdding
R6ding, Museum Boltenianui', pt. 2, p. 14, 1798. Type (logotype, Dall, U. S. Natl. Mus. Bull. 90, p. 109, 1915):
Helix haliotoidea Linn6 (cited by R6ding as Helix halioloidea
Gmelin), Recent, western Pacific(?).
The collections from the Gatuncillo formation, the marine member of the Bohio(?) formation, and the
413788-57-7


Caimito and Culebra formations include unidentified species of Sinum, represented by poorly preserved specimens. The Culebra Sinum may be the species from the Anguilla formation, of the island of Anguilla, recorded as Sinum chipolanum (Dall) (Cooke, 1919, p. 124, pl. 5, figs. 6a, 6b), but the species so identified is smaller and more depressed than S. chipolanum.
A species from the Gatun formation, Sinum gatunense (Toula) (1909, p. 697, pl. 28, figs. 3a, 3b, 3c) is not represented in the collections examined. It was compared by Toula with the Recent West Indian S. perspectivum (Say) and, according to his illustrations, is closely related to that species and the Recent Panamic S. noyesi Dall. Toula's species is greatly depressed and has a very narrow base. S. gatunense has been recognized in the Cercado formation of the Dominican Republic (Maury, 1917, p. 138, pl. 24, fig. 2) and in the Bowden formation of Jamaica (Woodring, 1928, p. 390, pl. 31, figs. 3, 4). S. dodonum Gardner (1926-47, p. 554, pl. 59, figs. 37, 39, 1947), of the Oak Grove sand member of the Shoal River formation of Florida, probably is a large form of S. gatunense. Though Toula's illustration shows no faint spirals on the base, some specimens of the species from the Dominican Republic and Jamaica identified as S. gatunense have faint basal spirals like those on the type of S. dodonum.
Sinum euryhedra Woodring, n. sp.
Plate 21, figures 4, 7, 10
Sinuan species, Woodring, Carnegie Inst. Washington Pub. 385, p. 390, 1928 (Miocene, Jamaica). Of medium size, moderately depressed, base relatively very wide. Protoconch consisting of about I1% smooth whorls. Spire whorls and body whorl between periphery and suture sculptured with spiral bands, separated by grooves that, for the most part, are of about same width as the bands, but near suture are twice as wide as the bands. Base smooth except for exaggerated growth lines. A narrow groove lies behind posterior part of everted columellar lip.
Height (incomplete, spire crushed) 11 mm, diameter (incomplete) 27 mm (type).
Type: USNM 561441.
Type locality: 137a (Stanford University locality 2655, Transisthmian Highway, 1.7 kilometers northwest of Sabanita, Panamd; same as USGS 16911), lower part of Gatun formation.
The type, an incomplete and somewhat crushed specimen collected from the lower part of the Gatun formation by T. F. Thompson, is the only representative of this species. It is characterized by moderate depression, wide base, and strong sculpture. Owing to crushing, the spire is too low in apertural aspect (pl. 21, fig. 4).


93






'1


GEOLOGY AND PALEONTOLOGY OF CANAL ZONE


94


There are no known close allies of this species in Caribbean and Panamic waters. S. maculatum (Say), a Recent Floridian and West Indian species, has a narrower base, thinner columellar lip and parietal callus, and weaker sculpture.
The small incomplete Sinum from the Miocene of Jamaica, so far as it goes, has the characters of S. euryltedra.
Occurrence: Lower part of Gatun formation (middle Miocene), locality 137a. Bowden formation (middle Miocene), Jamaica.
Sinum gabbi (Brown and Pilsbry) Plate 21, figures 3, 6
Sigaretus (Eunaticina) gabbi Bron and Pilsbry, Acad. Nat. Sci.
Phila. Proc., v. 64, p. 509, pl. 22, fig. 13, 1913 (Miocene,
Canal Zone).
Minum quirusanumn F. Hodson, Bull. Am. Paleontology, v. 13,
no. 49, p. 67, pl. 36, figs. 10, 12, 1927 [Miocene (OligoceneMiocene of Hodson), Zulia, Venezuela].
Reaching a large size, not depressed, body whorl strongly inflated. Spire low or relatively high. Protoconch of 2)) smooth slowly enlarging whorls. Sculpture of narrow closely spaced spiral threads of two or three orders. Spirals of early whorls variably crinkled by growth lines. A very narrow umbilical groove lies behind posterior part of everted columellar lip of adult shells. Immature shells umbilicate.
Height 23 mm, diameter 23 mm (figured specimen). Height 27 mm, diameter 24 mm (largest complete specimen). Estimated diameter 35 mm (largest specimen, incomplete).
Type: Acad. Nat. Sci. Phila. 3845.
Type locality: Gatun Locks excavation, Canal Zone, middle part of Gatun formation.
The type is a very small shell 6.5 millimeters high. The largest complete specimen (height 27 mm), collected at locality 175, has a higher spire than the others, but is associated with a smaller low-spired shell. That this species reaches a considerably larger size is shown by half of a body whorl (locality 176), which indicates a diameter of about 35 millimeters. The Venezuelan S. quirosanum is small, agreeing with S. gabbi in outline and sculpture, and may represent a small early Miocene race of S. gabbi. S. nolani Maury (1917, p. 139, pl. 24, fig. 1), a species that occurs in the Gurabo formation of the Dominican Republic, is more inflated than S. gabb.
S. gabbi is a nondepressed species related to the Recent Peruvian S. concavum (Lamarck), the largest species of the genus (height 48 mm). The fossils, except the high-spired specimen, have a similar outline, but have spirals of less uniform width. No similar species is living in the western Atlantic.


Occurrence: Middle and upper parts of Gatun formal. tion (middle Miocene). Middle part, eastern area localities 147b, 155, 155a, 155b, 155c (very small), 157 Upper part, eastern area, localities 175, 176, 177c.
Subfamily GLOBULARIINAE
Data concerning the anatomy of Cernina fluctuat (Sowerby), the only surviving globularine, are desirable as a basis for consideration of the subfamily or family status of that species and its numerous fossil allies.
Wrigley (1946, p. 88) has proposed a useful terminology for features in the umbilical region and on the columellar lip of globularines. The sheath (the limbe of French authors and the callus or fasciole of American authors) is the shell layer emerging from the umbilicus of umbilicated species. Its outer edge is designated the rim. The downward extension of the parietal callus, overlapping the sheath, is designated the lobe of the columellar border, or simply the lobe. The outer edge of the lobe, where it overlaps the sheath below the umbilicus, is either fairly sharp or indefinite.. The sheath of some nonumbilicated species, such as Globularia sigaretina (Lamarck), is as well defined as: that of umbilicated species, but the umbilicus is represented only by a slight depression at the posterior end of the sheath, formed by the outer edge of the lobe. On other nonumbilicated or narrowly umbilicated species a sheath is not recognizable. If present, it is concealed by the lobe, which forms an everted columellar lip that has an outer edge as sharp as a rim.
Genus Globularia Swainson
Swainson, A treatise on malacology, p. 345, 1840. Type (logotype, Herrmannsen, Indicis generum malacozoorum,
v. 1, p. 480, 1847): Natica sigaretina Lamarck, Eocene,
Paris basin.
Subgenus Globularia s.s.
Globularia (Globularia) aff. G. fischeri (Dall)
Plate 15, figures 9, 17, 18
Moderately large, weakly shouldered, greatly inflated. Spire low, turreted. A narrow sloping shelf lies between suture and shoulder. Aperture greatly expanded. Sheath moderately wide on immature specimens. Posterior part of lobe well defined on immature specimens. Umbilicus closed.
Height (almost complete) 35.5 mm, diameter 31 mm (large figured specimen). Height 18.5 mm, diameter (incomplete) 15.5 mm (small figured specimen).
This greatly inflated Globularia, represented by more or less incomplete and poorly preserved specimens from, the middle member of the Caimito formation of the Gatun Lake area and the Culebra formation, is closelyrelated to Globulariafscheri (Gardner, 1926-47, p. 556, pl. 59, fig. 28, 1947). G. fscheri occurs in the Chipola




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