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THE NEW YORK ACADEMY OF SCIENCES
SCIENTIFIC SURVEY
OF
PORTO RICO and the VIRGIN ISLANDS
VOLUME XVII-Part 1
The Pelecypoda or Bivalve Mollusks of Porto Rico and the
Virgin Islands
Richard A. McLean
NEW YORK
Published by the Academy
April 11, 1951
Editor
RoY WALDO MINER
Associate Editor
B. J. HENEGAN
SCIENTIFIC SURVEY OF PORTO RICO AND THE
VIRGIN ISLANDS
This natural history survey of Porto Rico and the Virgin Islands, conducted
by The New York Academy of Sciences, was established in 1913. Continuous
publication of the results of this survey is made possible through contributions
from the Department of Agriculture and Commerce of Porto Rico, and the Uni-
versity of Porto Rico.
Copyright, 1951, by The New York Academy of Sciences
THE PELECYPODA OR BIVALVE MOLLUSKS OF
PORTO RICO AND THE VIRGIN ISLANDS
By RICHARD A. MCLEAN
CONTENTS
INTRODUCTION 1
CLASSIFICATION OF THE PELECYPODA. 3
SYSTEMATIC AccoUNTr... 5
Order Prionodesmacea. 6
Order Anomalodesmacea. 46
Order Teleodesmacea. 51
REMARKS... 122
GLOSSARY 123
PLATES AND EXPLANATION OF PLATES. 127
INDEX 178
INTRODUCTION
The littoral pelecypod fauna of the Greater Antilles and of the West
Indian region as a whole is taxonomically well known. It is seldom that
collections from this area yield undescribed species. The distribution of
these forms, particularly the southern limit of their ranges, still requires
considerable study. Exact geographical records for the lower West Indies
and the northern Atlantic coast of South America are few and scattered.
From the cabinet collector's point of view, a fauna which does not yield
new forms is of limited interest. The fact is, however, that a phylum or
lesser group of animals must be well founded, taxonomically, before more
exact studies of evolution, speciation, and ecological influences can be
undertaken. Accordingly, the present work has been written in the nature
of a handbook of littoral bivalve mollusks. It may assist students to
investigate the dynamic processes which have produced these species and
which control them in their present environment.
The collections which have served as source material for this report
include those obtained from Porto Rico by The New York Academy of Sci-
ences and the American Museum of Natural History in expeditions during
the period from 1914 to 1925. Additional material was furnished by the
collections and observations of the author when on an expedition to Porto
Rico for Harvard University in the summer of 1937. The Museum of Com-
parative Zoology at Harvard and the Academy of Natural Sciences of Phila-
delphia have supplied many further records. Dall and Simpson's' report
has been a valuable source book. Considerable descriptive and diagnostic
I Bull. U.S. Fish Comm.20. 1901.
2 SCIENTIFIC SURVEY OF PORTO RICO
material has been derived from monographic works by Dr. W. H. Dall, Dr.
W. P. Woodring, and Dr. Julia Gardner.
Specific geographical records have not been identified as to source in the
text.
The keys are all original and are applicable to the particular fauna which
has been studied.
The author wishes to express his appreciation to Dr. Roy Waldo Miner,
editor of the New York Academy of Sciences, for the privilege of studying
the collections of the American Museum of Natural History which were
made as a part of the Scientific Survey of Porto Rico by The New York
Academy of Sciences, and for the opportunity of writing this report. Dr.
Henry A. Pilsbry, curator of mollusks at the Academy of Natural Sciences
of Philadelphia, has given invaluable advice and encouragement during the
preparation of the manuscript. The recommendations of Dr. Francis Har-
per have been very helpful.
The illustrations were made in the photographic department of the
Academy of Natural Sciences of Philadelphia, by Mr. A. D. Warden.
The index and explanation of the plates were prepared by my wife,
Virginia M. McLean, who has aided in many ways in bringing the manu-
script to completion.
CLASSIFICATION OF THE PELECYPODA
It is remarkable that the primary taxonomic divisions of a group of
animals, like the Pelecypoda, which is so numerous in individuals and
species and which can be traced back almost to the beginning of the fossil
record, still remain in a more or less tentative and uncertain state.
Two fundamental schemes underlie the divergent systems which are in
general use today. Pelseneer2 proposed a system based on anatomical
features, particularly the character of the gills. This scheme is of very
great interest to the student of bivalve mollusks, and the value of Pelseneer's
work is beyond question. However, there are a number of discrepancies
in the taxonomic groups as outlined by him. One of the most notable is
the separation of the Ostreidae, Pinnidae, and Limidae from the closely
related Pectinidae. This seems to be an artificial break in a continuous
evolutionary series. Fundamentally, the gills are a structure which ex-
hibit progressive evolution, that is, they can be traced through lineage and
show a definite trend in development. The danger inherent in a classifi-
cation of this kind is that it may place together members of different lineages
at the same grade of evolution, while members of the same lineage at
different grades are separated.
Neumayr3 proposed a classification based on hinge characters. These
appear to be stable characters which change slowly and may persist through
great modifications of life. Taken in conjunction with the relative develop-
ment of the adductor muscles, and subject always to checking by all other
features that are ascertainable, they afford good guidance to natural rela-
tionships. A system of this kind has the added advantage of permitting
comparisons with fossil forms ranging back through the phylogeny of the
recent species.
From Neumayr's classification, which has been subjected to various
modifications and changes, two systems have developed which, although
based on the same basic concepts, are sufficiently different to be regarded
as distinct taxonomic arrangements.
The first of these, and the most widely used, is that of Dall4, in which he
groups the bivalve mollusks in three orders and gives diagnoses of the
superfamilies and families assigned to each. There are anomalies in this
system as in the others, but, on the whole, it seems to be the most usable
at the present time.
The other system is that proposed by Douville5. This plan is favored
by Davies in his review of the bases of classification of the Lamellibranchia,6
and it has a very strong appeal to the present writer. It is certain that
Douvill6 had a clear, broad concept of evolutionary trends in the bivalve
mollusks. He did not propose formal names for his ordinal groups. The
2 Pelseneer, Paul. Arch. de Biol. 10. 1891.
Neumayr, M. Denkschr. K. K. Akad. Wiss. Wien, math. nat. Cl. 58. 1891.
Dall, W. H. Trans. Wagner Free Inst. Sci. Philadelphia 3 (3). 1895.
Douvilli. H. Bull. Soc. G6ol. France (4) 7. 1912.
Davies, A. Morley. Proc. Malac. Soc. London 20 (6). 1933.
4 SCIENTIFIC SURVEY OF PORTO RICO
three major divisions are based on a mode of life as reflected in the form of
the animal. The free-living forms make up one line. Another includes
those bivalves which are characteristically attached to the substratum by
a strong byssus, and the burrowing genera comprise the third. The chief
objection to this classification is that the ecological mechanism which is
supposed to have differentiated the orders is seen in evidence, on a minor
scale, within these same orders. At present, it seems difficult to reconcile
the sporadic occurrence of these three evolutionary trends throughout the
orders, each of which is supposedly based on only one of them.
Thiele7 has employed a scheme of classification which seems to be a
synthesis of those of Neumayr and Pelseneer. It will gain some accept-
ance as part of one of the few general synoptic works on the mollusks.
In the following systematic account of the marine bivalves of Porto
Rico and the Virgin Islands, the classification of Dall is employed. It seems
to be the most practical one available at this time. It is based upon broad
concepts and has fewer unexplained anomalies than any of the others.
However, future research may well establish at least some of Douvill's
scheme as an integral part of bivalve evolution and taxonomy.
7 Thiele. J. Handbuch der systematischen Weichtierkunde. Jena.
SYSTEMATIC ACCOUNT
Class Pelecypoda
The Pelecypoda are aquatic, bilaterally symmetrical mollusks protected
by a pair of shelly valves which are secreted by the lateral portions of the
mantle. The valves are united dorsally by a ligament and are moved by
muscles which connect their inner surfaces. There is no definite head.
Their food consists of minute particles of organic matter and microorganisms
which become entangled in mucus while passing over the gills with the
circulating water. These mucous strands and the included food are carried
along by a system of ciliary currents which run over the gills and forward
to the labial palps and thence to the mouth. Respiration is by gills and also
through the general surface of the integument. The circulatory system is
closed, although there are many large sinuses. The blood is usually nearly
colorless, and the respiratory pigment is usually hemocyanin. The heart
may have one or two ventricles and two auricles. There is a more or less
convoluted intestine, with its oral and anal extremities at opposite ends of
the body, and a well-developed stomach near the oral end. There are
paired kidneys, connected with the pericardium and discharging independ-
ently of the rectum. Reproduction is by eggs and spermatozoa without
copulation. The animals may be monoecious or dioecious. Development
is external to the genital tract. The postlarval young are protected by a
prodissoconch and sometimes exhibit a nepionic stage. The nervous system
is usually composed of three principal pairs of ganglia, united by nerves.
The Pelecypoda are imperfectly sensitive to light, although occasionally
provided with peripheral sense organs and, sometimes, with a light-sensitive
pigment in the tissues of the siphons. They have tactile papillae, olfactory
organs (osphradia), and auditory and equilibrating organs (otocysts).
There are three major subdivisions or Orders of the Class.
Brief, comparative diagnoses of the three orders follow.
Order PRIONODESMACEA
(1) Shell substance nacreous and prismatic, rarely porcellaneous.
(2) Area amphidetic or obscure, rarely divided into lunule and escutcheon; when so
divided, having an amphidetic ligament.
(3) Ligament variable, rarely opisthodetic.
(4) Hinge plate variable.
(5) Hinge teeth absent or obscure, taxodont, isodont, dysodont, or amorphous schizo-
dont.
(6) Byssus present or absent, frequently used for firm fixation by adults.
(7) Mantle lobes separated or, when caught together, with imperfectly developed
siphons.
(8) Adductor muscles equal, or anterior one reduced, obsolete or absent.
Order ANOMALODESMACEA
(1) Shell substance nacreous and porcellaneous, rarely prismatic.
(2) Area amphidetic or obscure, rarely distinctly divided.
(3) Ligament usually opisthodetic, generally associated with an internal resilium,
chondrophores, and a lithodesma.
SCIENTIFIC SURVEY OF PORTO RICO
(4) Hinge plate not developed.
(5) Hinge teeth often obsolete or absent, rarely with lateral laminae or well-developed
dental processes.
(6) Byssus present or absent.
(7) Mantle lobes more or less completely united, with a pedal opening and sometimes
an opisthopodial opening in addition to the two well-developed siphons.
(8) Adductor muscles subequal.
Order TELEODESMACEA
(1) Shell substance porcellaneous or obscurely prismatic, never nacreous.
(2) Area, if present, always prosodetic, or divided into lunule and escutcheon.
(3) Ligament opisthodetic, with or without a separate resilium, without a lithodesma,
rarely with external accessory shelly pieces.
(4) Hinge plate usually well developed.
(5) Hinge teeth differentiated into distinct cardinals and laterals; the posterior laterals,
when present, are behind the ligament. Rarely, in boring forms, the hinge is prac-
tically edentulous but supplemented by external shelly plates.
(6) Byssus present or absent, seldom functional in adults.
(7) Mantle lobes generally more or less connected, forming well-developed siphons.
(8) Adductor muscles typically subequal.
No key was prepared for the orders, as it is difficult to find a single char-
acter, or even two or three, that will separate all members of one major
group, without exception, from all members of another. Specialization,
convergent evolution or degeneration will often cause members of unlike
phylogenies to approximate one another in form or appearance. Sub-
ordinal groups and all lower categories have been provided with keys.
Order PRIONODESMACEA
Five subordinate groups of this order seem to have followed definite and
distinct trends of evolution and are ranked as suborders.
KEY TO THE SUBORDERS OF PRIONODESMLACEA
(1) Hinge edentulous; periostracum heavy and conspicuous, extending beyond the
valve margins. .Edentulata
(1') Hinge not edentulous or, if apparently edentulous, then periostracum not as
outlined in (1) (2)
(2) Hinge teeth numerous, serial, reduplicated along hinge margin; ligament seldom
parivincular, but, when so formed, then the teeth are divided into two groups,
one on either side of the umbones. Taxodonta
(2') Hinge teeth and ligament not as described in (2). .(3)
(3) Hinge teeth concentrically arranged. .Isodonta
(3') Hinge teeth not concentrically arranged.. .(4)
(4) Hinge teeth schizodont, sometimes obsolete; ligament usually multivincular or
alivincular, rarely parivincular; if hinge teeth are obsolete and ligament pari-
vincular, then shell gaping widely behind. .Schizodonta
(4') Hinge teeth dysodont or obsolete; ligament parivincular; shells not widely gaping
Dysodonta
Suborder EDENTULATA
The shell is thin, elongate, practically equivalve, low-beaked, with a
conspicuous epidermis, substance prismatic. The hinge is edentulous.
Mantle lobes are united ventrally, and anal and branchial openings are not
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
separated. The gills are foliobranchiate. The pleural ganglion is distinct.
Both adductors are present. These animals are not byssiferous.
Family SOLEMYIDAE
The shell is soleniform, gaping, with the anterior end longer and the
epidermis conspicuous, extending beyond the valves. The area is obscure
or absent. The ligament is amphidetic, parivincular, becoming internal
posteriorly. The mantle lobes are attached, in front, to the epidermis and
valves by a broad surface, leaving no distinct pallial line. There is a
single posterior siphonal and anterior pedal opening in the mantle. The
palpi are united laterally above. Adductors are subequal, with a thickened
ray in front of the posterior scar. The ventricle embraces the rectum and
gives out a single anterior aorta. The foot is elongated, having a pedal
gland, but no byssus, with a terminal groove which may be expanded to a
stellate disk.
Genus SOLEMYA Lamarck
Solemya Lamarck (1818) Anim. s. Vert. 5: 488.
Solenimya Bowdich (1822) Elem. Conch. 2: 8.
Solenomya Children (1823) Quart. J. Sci. 14: 300.
Solenymia Swainson (1840) Treat. Malacol. 366.
Solenymya Schauluss (1869) Moll. Syst. Cat. Paetel 21.
TYPE. (by subsequent designation, Children 1823), Solemya mediterranea Lamarck.
The characters of the genus are the same as given for the family.
There is one species of Solemya in this fauna, and it is properly placed in
Dall's subgenus Petrasma.
Subgenus PETRASMA Dal
Petrasma Dall (1908) Nautilus 22 (1): 2.
TYPE (by original designation), Solemya borealis Totten.
Differs from the typical members of the genus in not having the ligament
exposed internally in front of the chondrophore.
Solemya (Petrasma) occidentalis (Deshayes)
PLATE 1, FIGURE 1
Solenomya occidenlalis Deshayes (1858) J. Conchyl. 7: 186. PI. 7, fig. 6.
This species has the chondrophore with an anterior prop or buttress
extended as a slender rib in front of the adductor scar. There is no posterior
prop. The periostracum is of a light corneous color.
Length 18.5, height 6, width 3 mm.
Porto Rico: One specimen from Porto Rico, without specific locality data,
in the collections of the Survey.
Suborder TAXODONTA
The dentition is taxodont, consisting of a repetition of similar teeth
along the hinge line. The ligament may be alivincular, multivincular, or
parivincular; but, if parivincular, then the teeth are divided into two
SCIENTIFIC SURVEY OF PORTO RICO
separate groups, one before and one behind the umbones. There are two
subequal adductors.
There are two distinct groups in this suborder, the superfamily Nuculacea
and the superfamily Arcacea.
KEY TO THE SUPERFAMILIES
(1) Shell substance often nacreous; area obscu e or divided into lunule and escutcheon;
teeth usually chevron-shaped; not hyssiferous. Nuculacea
(1') Shell substance not nacreous; area amphidetic; teeth rarely chevron-shaped;
usually byssiferous. .Arcacea
Superfamily NUCULACEA
The Nuculacea have an equivalve shell of varied form. The epidermis
is smooth and often greenish in color. Under the epidermis, there is a
tubuliferous prismatic layer. The valves may have a pearly or porcellanous
lining. The hinge area is usually obscure but, when present, is divided into
a lunule and an escutcheon. The ligament extends on either side of the
beaks and may be in the form of a single stout band (alivincular) or a
short "C" spring (parivincular). The dentition of the hinge consists of a
series of similar teeth, alternating on each side of the hinge margin. The
pallial line may be simple or sinuate, depending on the absence or presence of
siphons. Both adductors are present and subequal. These forms do not
have a byssus.
There are two families represented in this fauna.
KEY TO THE FAMILIES OF NUCULACEA
(1) Ends of the shell tightly closed, no siphons, pallial line simple.. Nuculidae
(1') Ends of the shell usually partly gaping, complete siphons, pallial line usually
sinuate. .Nuculanidac
Family NUCULIDAE
The shell is compact, closed, with the teeth in two series meeting below
the umbones and separated by a chondrophore. The area is represented
by an obscure lunule and escutcheon. There is no ligament, but a wholly
internal, amphidetic, alivincular resilium. The internal layer of the shell
is nacreous. The pallial line is usually simple and the mantle lobes free,
without siphons. The ventricle is sub-duplex, dorsal to the rectum, with
anterior and posterior aortas.
Genus NUCULA Lamarck
Nucula Lamarck (1799) Mem. Soc. Hist. Nat. Paris -: 87.
TYPE (by monotypy), Area nucleus Linnaeus.
The shell is small, trigonal, inequilateral, with the anterior end longer
than the posterior. The interior is nacreous. The area behind the umbo
is slightly or strongly depressed. The surface is smooth or sculptured with
fine radials or concentric rugae or both. The chondrophore is narrow and
oblique. The hinge consists of anterior and posterior series of chevron-
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
shaped teeth, the anterior one longer. Lower margin of the valve is fre-
quently finely fluted.
Nucula aegeeinsis Jeffreys
PLATE 1, FIGURE 4
Nucuta aegetnsis Jeffreys (1879) Proc. Zool. Soc. London, -: 581.
The shell is rather small, thin, and nearly regularly ovate. It is slightly
oblique, uniformly convex, and has a low, rounded posterior ridge. The
straight umbones project but little beyond the rest of the shell. The
sculpture is made up of exceedingly fine concentric ridges. The rather
broad hinge is armed with few teeth, and the cartilage pit is small. This
species is close to N. lenuis Montagu.
Length 10.7, height 8, width 4.7 mm.
Family NUCULANIDAE
The shell is similar to the Nuculidae, but with the ligament variable and
the resilium sometimes external, or absent. The internal layer is sub-
nacreous or porcellanous. The ends of the shell are partly gaping. The
pallial line is usually sinuated, with the mantle lobes more or less united,
and with complete, sometimes elongate, siphons. The ventricle embraces
the rectum and has both anterior and posterior aortas.
KEY TO THE GENERA OF NUCULANIDAE
(1) Resilium located in the hinge line dividing the teeth into two series. .Nuculana
(1') Resilium above the hinge line, teeth sometimes divided by a blank space but
not by a chondrophore. .Tindaria
Genus NUCULANA Link
Nuculana Link (1807) Beschr. Nat. Samml. Univ. Rostock 3:
Leda Schumacher (1817) Nouv. Syst. Vers Test -: 55.
TYPE (by monotypy). Arca rostrata Chemnitz = Nuculana roslrata Link.
The shell is medium-sized, elongate, inequilateral, with the posterior
end rostrate and slightly gaping. The rostrum is bicarinate. The lunule
is distinct. The sculpture consists of concentric rugae on the dorsal half
of the valve, replaced by incrementals on the ventral half. The hinge
consists of an anterior and posterior series of chevron-shaped teeth, with the
posterior series almost twice as long as the anterior series. The chondro-
phore is small, deep, and triangular. The pallial sinus is shallow with its
apex narrowly U-shaped.
Nuculana acuta (Conrad)
PLATE 1, FIGURE 2
Sucula acula Conrad (1831) Am. Mar. Conch. -: 32, Pl. 6,f. 3.
Leda cuneala Sowerby (1832) Proc. Zool. Soc. London -: 198.
Leda jamaicensis d'Orbigny (1845) Moll. Cubana 2: 262. PI. 26, f. 27-29.
Leda unca Gould (1862) Proc. Boston Soc. Nat. Hist. 8: 282.
Leda inornata A. Adams, fide Hanley from type.
SCIENTIFIC SURVEY OF PORTO RICO
The sculpture of this species is quite variable. It may be finely con-
centrically ridged or coarsely waved, but, typically, the concentric ridges
are moderate and regular, becoming obsolete towards the ends and base.
Length 9, height 5, width 3.5 mm.
Porto Rico: Mayaguez.
Genus TINDARIA BeUardi
Tindaria Bellardi (1875) Monogr. Nuculidi Terr. Terz. Piemonte Liguria -: 28.
Type (by monotypy), Tindaria arala Bellardi.
The shell is solid, closed, and concentrically sculptured. The ligament
and resilium are amphidetic and outside the hingeplate or line of teeth.
The pallial line may be feebly waved or entire.
Subgenus NEILONELLA Dall
Neilonella Dall (1881) Bull. Mus. Comp. Zool. 9: 126.
TYPE (by monotypy), Leda (Nielonella) corpulenta Dall.
The shell is attenuate behind with the ligament long; the resilium short,
central, and in a socket above the tooth line. The teeth are divided into
two series by a space below the resilium. The pallial line is feebly waved.
Tindaria (Neilonella) corpulenta (Dall)
PLATE 1, FIGURE 3
Leda (Neilonella) carpulenta Dall (1881) Bull. Mus. Comp. Zool. 9: 125.
The lunule and escutcheon are very faintly defined. There are about
15 teeth on each side of the beaks. The shell substance is porcellaneous
with a light olive, polished epidermis.
Length 10, height 6.5, width 4.5 mm.
Porto Rico: Mayaguez.
Superfamily ARCACEA
In the Arcacea, the shell is varied in form. There is usually a pilose
epidermis. The shell substance is largely porcellaneous, with a tubuli-
ferous, non-prismatic, outer layer and no nacreous layer. The hinge area
extends on either side of the beaks. The ligament is external and may
consist of one band running from beak to beak across the hinge line (alivin-
cular) or of several similar bands transverse to this line (multivincular).
The dentition consists of alternating serial teeth. The pallial line is simple.
The adductor muscles are both present and subequal. A byssus is usually
developed.
There are two families in this region.
KEY TO THE FAMILIES or ARCACEA
(1) Shell circular or very nearly so; teeth in two nearly equal groups; animals free-
living, with no byssus.. Glycimeridae
(1') Shell not usually circular; teeth frequently in unequal groups; animals typically
attached by a byssus......................................... Arcidae
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Family GLYCIMERIDAE
The shell is circular, equivalve, and practically equilateral. The hinge
and ligament are similar to the Arcidae with the two groups of teeth nearly
equal on either side of the beaks. The area may be amphidetic or opistho-
detic. The principal surface sculpture is radial, although some forms are
nearly smooth. The soft parts are similar to the Arcidae. The animals are
free-living, without a byssus.
Genus GLYCIMERIS da Costa
Glycimeris da Costa (1778) Hist. Nat. Test. Brit. -: 168.
TYPE (by autonomyy, Area glycimeris Linnaeus.
The shell is medium-sized, suborbicular, and equilateral, with the um-
bones erect or prosogyrous. Sculpture consists of radial striae or radial
ribs. The hinge area is moderately wide with the ligament amphidetic or
opisthodetic. The hinge consists of two series of heavy teeth, outer teeth
of both series almost horizontal, inner teeth chevron-shaped, median teeth
obliterated by a downward extension of the hinge area. The inner surface
of the margins of the valves are fluted. The byssus is absent in the adult.
KEY TO THE SUBGENERA OF Glycimeris
(1) Umbones erect, ligament amphidetic ..... .Glycimeris s.s.
(1') Umbones prosogyrous, ligament opisthodetic................. .Glycimerdella
Subgenus Glycimeris s.s.
The description is as given under the genus with the restrictions of erect
umbones and amphidetic ligament.
KEY TO THE SPECIES OF Glycimeris s.s.
Radial ribs rounded, numbering more than thirty; anterior end not attenuate..
C. pectinatus
(1') Radial ribs flattened, numbering less than thirty; anterior end somewhat attenuate
G. sericatus
Glycimeris (Glycimeris) pectinatus (Gmelin)
PLATE 1, FIGoRE 8
Arca pcctinatla Gmelin (1792) Syst. Nat., Ed. 13: 1313.
This species is somewhat more regular in outline and more rugose than
the following species.
Length 32.5, height 31.5, width 18 mm.
Porto Rico: Mayaguez; Guanica.
Virgin Islands: St. Thomas; St. Croix; Caneel Bay, St. John; Tortola;
Virgin Gorda.
Glycimeris (Glyclmeris) sericatus (Reeve)
PLATE 1, FIGURE 6
Pectunculus sericalus Reeve (1843) Proc. Zool. Soc. London -: 190.
SCIENTIFIC SURVEY OF PORTO RICO
This is a broadly ribbed, rather flattened species with a silky epidermis.
Length 35.5, height 34.5, width 19 mm.
Porto Rico: Ponce.
Virgin Islands: St. Thomas; Tortola; St. Croix.
Subgenus GLYCIMERELLA Woodring
Glycrimerella Woodring (1925) Publications Carnegie Inst. Washington 366: 26.
TYPE (by original designation), Pectunculus pennaceus Lamarck.
The shell is medium-sized, suborbicular, and slightly inequilateral with
the umbones inflated and prosogryrate. The sculpture consists of narrow
radial ribs, radial striae, and fine concentric threads. The hinge area is
narrow and excavated with the ligament opisthodetic. The hinge is made
up of two continuous series of chevron-shaped teeth, the posterior series
convex, the anterior series almost straight. The upper edge of inner poste-
rior teeth is obliterated by the ligament. The inner margins of the valves
are fluted.
Glycimerls (Glycimerella) pennaceus (Lamarck)
PLATE 1, FIGURE 5
Pectunculus pennaceus Lamarck (1819) Anim. s. Vert. 4:
This is a moderately large species with a characteristic sculpture of fine
radial lines. It is variously spotted with chestnut brown. The epidermis
is frequently preserved in the interstices of the fine radial sculpture, giving
the appearance of colored lines. It bears a very close superficial resemblance
to G. lineatus Reeve, but the hinge of this species places it in the typical
subgenus.
Length 48, height 47, width 30 mm.
Porto Rico: San Juan; Boqueron Bay; Culebra; Vieques.
Virgin Islands: St. Thomas; Tortola; Virgin Gorda.
Family ARCIDAE
The shell is trapezoidal or rounded, with the posterior side longer and
the ligament usually multivincular. The hinge is typically taxodont, with
the teeth in two similar series, meeting below the beaks and approximately
vertical to the margin of the valves. The ventricle is more or less double,
and dorsal to the rectum. The foot is short, stout, and deeply grooved.
The species are generally byssiferous.
Only the typical genus is represented in the material studied for this
report. However, several deep-water genera are known from the West
Indian region and may, eventually, be found in this area.
Genus ARCA Linnaeus
Area Linnaeus (1758) Syst. Nat. (Ed. 10): 693.
TYPE (by subsequent designation, Gray, 1847), Area nose Linnaeus.
The shell is variable, rounded or quadrate, often strongly inflated, inequi-
lateral, with the anterior end shorter and the sculpture radial. The ribs
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
are sometimes beaded or cancellate. The area is amphidetic or opistho-
detic, with the ligament alivincular or multivincular. The hinge is typically
taxodont, in two series, more or less plainly delimited under the umbones.
The individual teeth are fundamentally chevron-shaped, but the lower
branch of the chevron is frequently absent. The anterior muscle scar is
rounded, the posterior scar larger and rectangular. The inner margin is
variously crenulate or fluted. The byssus is strong and functional.
There are five subgenera in this region.
KEY TO THE SUBGENERA OF Arca
(1) Ligament opisthodetic. (2)
(1') Ligament amphidetic. .(3)
(2) Hinge teeth in two subequal groups. .Acar
(2') Anterior group of hinge teeth much reduced and irregular .Arginarca
(3) Margin deeply and regularly fluted. .Scapharca
(3') Margin irregularly fluted or crenulate, sometimes almost smooth. .(4)
(4) Hinge area wide; beaks high and inflated; teeth relatively regular and very numer-
ous; margin smooth, with crude folds corresponding to the larger ribs. Arca s.s.
(4') Hinge area moderately narrow; beaks lower and not inflated; teeth reduced
beneath the umbones, becoming larger distally, less numerous than in preceding
group; margin irregularly fluted or crenulate. .Barbatia
Subgenus ARCA s.s.
The shell is large, inequilateral, inflated, with the posterior end keeled
and the area very broad and flattened, The sculpture is irregular, ribbed
or beaded. The ligament is amphidetic. The hinge teeth are small, very
numerous and regular, the series scarcely interrupted below the umbones.
The margins of the valves are smooth except for crude amorphous folds
corresponding to the larger ribs. There is a moderate to large byssal gape.
KEY TO THE SPECIES OF Arca s.s.
(1) Sculpture consisting of strong ribs anteriorly and posteriorly, median area less
strongly ribbed; plainly striped with brown. .A. occidentalis
(1') Sculpture consisting of low beaded ribs more or less uniform over the whole shell;
irregularly suffused and clouded with brown. A. umbonata
Arca (Arca) occidentalis Philippi
PLATE 1, FIGURE 7
Arca occidenlalls Philippi (1847) Abbild. & Beschr. 3: 14, P1. 17, B, figs. 4a-c.
This is a large, plainly marked species. Its ribbing and coloration make
it easy to distinguish from all other species of this region.
Length 90, height 40, width 50 mm.
Porto Rico: Mayaguez; Ponce; Guanica; Playa de Humacao; Boca de
Cangrejos; San Geronimo; Arroyo; Punta Melones; Parguera; Tallaboa
Bay.
Virgin Islands: St. Thomas; Caneel Bay, Flannagans Passage, St. John;
Tortola; Virgin Gorda.
SCIENTIFIC SURVEY OF PORTO RICO
Arca (Arca) umbonata Lamarck
PLATE 2, FIGURE 1
Arca umbonata Lamarck (1819) Anim. s. Vert. 6: 37.
The more uniform sculpture and fine beading separate this species from
the preceding. It is very irregular in shape, apparently as a result of
environmental influences.
Length 50, height 20, width 20 mm.
Porto Rico: San Juan, Mayaguez, Guanica, Boca Prieta; Porto Real;
Boca de Cangrejos; N. of Vega Baja; Mona Id.
Virgin Islands: Charlotte Amalie, St. Thomas; Caneel Bay, Flannagans
Passage, St. John; St. Croix; Tortola; Virgina Gorda.
Subgenus BARBATIA Gray
Barbatia Gray (1847) Proc. Zool. Soc. London, Pt. 15: 197.
TYPE (by original designation), Arca barbata Linnaeus.
The shell is medium-sized, inequilateral, equivalve, usually rather com-
pressed laterally, with the posterior end rounded and the area moderately
narrow. The sculpture consists of fine radial ribs. The ligament is amphi-
detic. Hinge teeth are in two series, the anterior group smaller but well
developed. The margins of the valves are finely fluted or crenulate. The
byssal gape is moderately small.
There are three species of this group in the region.
KEY TO THE SPECIES OF Barbatia
(1) Shell substance white. .(2)
(1') Shell substance brown. ............... A rca barbata
(2) Shell flattened, irregular; ribs coarsely beaded... Arcacandida
(2') Shell tumid, trapezoidal, ribs fine and thread-like.. .Arca tenera
Arca (Barbatia) barbata Linnaeus
PLATE 2, FIGURE 3
Arca barbala Linnaeus (1758) Syst. Nat. (Ed. 10): 693.
This is a smooth rounded species not readily confusable with any other
species occurring in the region.
Length 50, height 28, width 17 mm.
Porto Rico: Guanica; Fajardo; San Geronimo; Liaza Vieja; Boca de
Cangrejos; Ensenada Honda, Culebra; Caballo Blanco Reef, Vieques.
Virgin Islands: Lindbergh Beach, Charlotte Amalie, St. Thomas; Tortola;
Virgin Gorda.
.Arca (Barbatia) candida Gmelin
PLATE 2, FIGURES 6 AND 8
Arca candida Gmelin (1792) Syst. Nat. (Ed. 13):
This is a white species with a heavy brown periostracum. The outline
and general form of this species are extremely variable, but the coarse
beaded ribs and color serve to distinguish it from the others.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Length 60, height 35, width 28 mm.
Porto Rico: San Juan; Mayaguez; Ponce; Puerto Real.
Virgin Islands: St. Thomas; St. Croix; Caneel Bay, St. John; Tortola;
Virgin Gorda.
Area (Barbatia) tenera C. B. Adams
PLATE 2, FIGURE 2
Arca lenera C. B. Adams (1845) Proc. Boston Soc. Nat. Hist. 2: 9.
Arca (Barbalia) balesi Pilsbry and McLean (1939) Notulae Naturae Acad. Nat. Sci. Phila. 39: 1, text fig.
This fine small species is quite distinct from the others. Its tumid and
trapezoidal shape and fine thread-like ribs are good characters. It has
somewhat the appearance of an Acar, but the hinge is that of Barbatia.
It was named as new by the author together with Dr. Pilsbry. Some years
earlier, the author had segregated this species as unnamed in the collections
of the Museum of Comparative Zoology. It was also unnamed in the
collections of the Academy of Natural Sciences of Philadelphia. However,
Adams' original material came to light when his collection was moved to
Harvard University, and Arca balesi is without question his unfigured
species.
Length 35, height 23.5, width 19 mm.
Virgin Islands: Tortola.
Subgenus ACAR Gray
Acar Gray (1847) Ann. Mag. Nat. Hist. (2) 19: 369.
TYPE (by subsequent designation, Woodring, 1923), Arca gradata Brod. and Sowb.
The shell is small, inflated, trapezoidal, equivalve, with the posterior end
keeled and the area narrow. The sculpture is reticulate and imbri-
cate. The ligament is opisthodetic. Hinge teeth are in two subequal
series, the anterior one somewhat smaller. The margins of the valves
are moderately fluted except at the byssal gape, which is small.
KEY TO THE SPECIES OF Acar
(1) Sculpture coarsely reticulate................ ............... ..... A. reticulata
(1') Sculpture very finely cancellate ........................... .... A. adanmsi
Arca (Acar) reticulata Gmelin
PLATE 2, FIGURE 5
Arca reliculata Gmelin (1792) Syst. Nat. (Ed. 13): 3311.
This species is coarsely reticulate. The posterior end is frequently some-
what attenuate, and the shell is quite variable in form.
Length 20, height 11, width 9 mm.
Porto Rico: San Juan; Mayaguez; Ponce; Guanica; Hucares; Boca de
Cangrejos; Caballo Blanco Reef, Vieques.
Virgin Islands: Charlotte Amalie, St. Thomas; St. Croix; St. John.
SCIENTIFIC SURVEY OF PORTO RICO
Area (Acar) adamsi Smith
PLATE 2, FIGuRE 4
Arce (A car) adamsi Smith (1888) J. Linnean Soc., Zool. 20: 499, Pl. 3, jigs. 6-6a.
The sculpture is finely cancellate. The shell is trapezoidal, tumid, and
quite regular in form.
Length 12, height 7.5, width 7.5 mm.
Porto Rico: San Juan; Mayaguez; Ponce; Aguadilla; Vieques.
Virgin Islands: Charlotte Amalie, St. Thomas; Tortola; Virgin Gorda.
Subgenus SCAPHARCA Gray
Scapharca Cray (1847) Proc. Zool. Soc. London, Pt. 15: 198.
TYPE (by original designation), Arca inacquivalvis Bruguitre.
The shell is medium-sized to large, inequilateral, sometimes inequivalve,
with the posterior end frequently keeled and, usually, strongly inflated.
The area is narrow or broad. The sculpture is strongly ribbed and the
ligament amphidetic. Hinge teeth are in two functional series, the anterior
one smaller than the posterior but regular and vertical to the hinge line.
The margins of the valves are deeply fluted and not gaping.
KEY TO THE SPECIES OF Scapharca
(1) Shell length distinctly greater than height. (2)
(1') Shell length about equal to height. A. chemnitzi
(2) Ribs about thirty in number. (3)
(2') Ribs about thirty-five in number A. secticoslata
(3) Shell rounded, hinge apparently somewhat curved, posterior slope convex
A. transversa
(3') Shell auriculate, hinge markedly straight, posterior slope concave. .A. auricidata
Area (Scapharca) aurlculata Lamarck
PLATE 2, FIGuRE 9
Arca auriculala Lamarck (1819) Anim. s. Vert. 6: 43.
Arca deshayesi Hanley (1842) Ill. Cat. Bivalve Shells -:
This is a heavy, tumid shell, auriculate both anteriorly and posteriorly.
The hinge line is very straight, and the ribs are strong and clearly delimited.
The umbones are higher than those in A. transversa.
Length 65, height 45, width 45 mm.
Porto Rico: San Juan; Mayaguez; Ponce; Vieques.
Virgin Islands: Lindbergh Beach, Charlotte Amalie, St. Thomas.
Area (Scapharca) transversa Say
PLATE 3, FIGURE 3
Arca transrersa Say (1822) J. Acad. Nat. Sci. Philadelphia 2; 269.
This species is more rounded than the preceding one and gives the im-
pression of being more compressed laterally, although extreme specimens
are much the same in general form. The ribbing is less pronounced and
the hinge line appears curved. It is sometimes slightly auriculate but not
to the extent of A. auriculata. It is a smaller species.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Length 30, height 21, width 16 mm.
Virgin Islands: Charlotte Amalie, St. Thomas.
Area (Scapharca) secticostata Reeve
PLATE 3, FIGURE 2
Arcsa seclicosjtla Reeve (1844) Conch. Icon. 2, Arcs fig.
Arca lienosa of authors, not Say.
Anomalocardia floridana Conrad (1869) Am. J. Conch. 5: 108, PI. 13, fig. 2.
This is a large species not readily confusable with the others. It has
more numerous ribs than either of the two preceding ones and is noticeably
longer in proportion to its height. The ribbing is strong and distinct.
Length 85, height 52, width 52 mm.
Porto Rico: Mayaguez.
Area (Scapharca) chemnitzi Philippi
PLATE 2, FIGURE 7
Arca chemnitzi Philippi (1851) Z. f. MAala. 8: 50.
Arcsa d'orbignyi Kobelt (1891) Conch, Cab. 2: 57, Pl. 16, figs. 7-8.
This is a short, tumid species, its height being nearly equal to its length.
The umbones are very high and inflated, and the area is correspondingly
broad. The ribs are distinct. The anterior ones are always beaded, and
sometimes those of the disk and the posterior part as well.
Length 30, height 30, width 30 mm.
Porto Rico: San Juan; Mayaguez; Ponce; Humacao; Boqueron Bay;
Culebra; Vieques.
Virgin Islands: Charlotte Amalie, St. Thomas.
Subgenus ARGINARCA new name
Argina Gray (1840) Syn. Cont. Brit. Mus. (Ed. 42): 151 (nude name).
Argina Gray (1842) op. cit. (Ed. 44): 81 (not Huebner, 1819).
Argina Gray (Adams, 1858) Genera Rec. Moll. 2: 540.
TYPE, Arca (Arginarca) campechiensis Gmelin.
The shell is medium-sized to large, rounded and inflated. The area is
relatively narrow and the sculpture strongly ribbed. The ligament is
opisthodetic. The hinge teeth are in two unequal series, the anterior group
much reduced and irregular. The margin of the valves is deeply fluted,
not gaping.
Arcsa (Arginarca) campechiensis Gmelin
PLATE 3, FIGURE 1
Arca campechiensis Gmelin (1792) Syst. Nat. (Ed. 13): 3312.
Arca pexata Say (1822) J. Acad. Nat. Sci. Phila. 2: 268.
Arcs americana Wood (1828) Index Test. Suppl., P1. 2, Arcs fig. 1.
Area holmesii Stimpson (1860) Smithson. Inst. Checklist -: 2.
This species is apparently capable of considerable variation under the
influence of its environment. It ranges from New England to South
America. It may be rounded or elongate, and of a chalky consistency or
SCIENTIFIC SURVEY OF PORTO RICO
porcellaneous, depending on the ecological conditions where it is found.
There is a discrepancy in sculpture between the valves: the ribs of the left
valve are narrower, flatter, and less prominent than those of the right and
are frequently grooved down the middle, while those of the right are not
grooved. Some specimens are inequivalve, the left valve overlapping the
right. Typical specimens of campechiensis are the rounded southern form.
A. holmesii is also based on this variation. A. americana is an elongate,
quadrate, porcellaneous form, such as is common on the Carolina coast.
Say's pexata could be either, but as described by Gould in 1841 it applies to
the chalky northern form. The variation in form and sculpture is wide
and does not seem to have a geographical correlation, so that it seems inad-
visable, at the present time, to give the extreme variants subspecific or
varietal names.
Length 36, height 27, width 24 mm.
Porto Rico: San Juan; Mayaguez; Aguadilla.
Virgin Islands: St. Thomas.
Suborder SCHIZODONTA
The shell is of varied form, with the inner layer frequently nacreous or
subnacreous and the area amphidetic or opisthodetic. The ligament may
be alivincular, multivincular, or parivincular. The hinge is schizodont or
edentulous. If the hinge is edentulous and the ligament parivincular, then
the shell is gaping widely behind. The adductor muscles may be subequal,
or the anterior adductor may be reduced or absent. A byssus is usually
present, sometimes only in the larval stages. There is frequently a distinct
nepionic stage.
KEY TO THE SUPERFAMILIES OF SCHIZODONTA
(1) Shell sessile, cemented to the substratum. ....................Ostracea
(1') Shell not sessile, frequently attached by a byssus..... ............ Pteriacea
Superfamily PTERIACEA
The shell is of varied form, frequently alate, with a nacreous or subna-
creous inner and a prismatic outer layer. The epidermis is seldom conspicu-
ous. The area is amphidetic, with the ligament variable, usually not pari-
vincular. The hinge is schizodont or edentulous; the gills are filibranchiate
or reticulate, usually reflected. The mantle lobes are free, without siphons,
and the pallial line is simple. The anterior adductor is smaller, or fre-
quently obsolete, in the adult, though present in the young. The species
are generally byssiferous. The young sometimes show a distinct nepionic
stage.
KEY TO THE FAMILIES OF PTERIACEA
(1) Shell dimyarian. .Pinnidae
(1') Shell monomyarian. (2)
(2) Ligament alivincular. Pteriidae
(2') Ligament multivincular ............................ Isognomonidae
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Family PINNIDAE
The shell is mytiliform, not'alate, dimyarian with the anterior adductor
smaller. It is equivalve, truncate, and wholly open behind. The hinge is
edentulous, the area linear with the ligament parivincular and internal.
The shell structure is coarsely prismatic, with a thin, partial, nacreous
lining. The ventricle embraces the rectum, with both anterior and poste-
rior aortas. The gills are reticulate and plicate, with direct and reflected
laminae, and free distal borders. The foot is conical, elongate, and grooved.
There is a profuse, silky byssus. The anal end of the rectum is free and
erectile.
KEY TO THE GENERA OF PINNIDAE
(1) Shell cleft by a median sulcus occupied by cartilage........... Pinna
(1') Shell not cleft by a median sulcus.................. ................ Atrina
Genus PINNA Linnaeus
Pinna Linnaeus (1758) Syst. Nat. (Ed. 10): 707.
TYPE (by subsequent designation, Gray, 1847), Pinna rudis Linnaeus.
The shell is large, thin, elongate, trigonal, and gaping at the posterior
end. The umbones are terminal. The exterior bears a longitudinal groove
at the angular shoulder. The sculpture consists of longitudinal ridges.
The hinge is edentulous. The inner nacreous layer is cleft opposite the
shoulder, except near the umbo, where there is a narrow ridge.
Pinna rudis Linnaeus
PLATE 3, FIGURE 5
Pinna rudis Linnaeus (1758) Syst. Nat. (Ed. 10): 707.
Pinna cornea Gmelin (1792) Syst. Nat. (Ed. 13): 3365.
Pinna flabellum Reeve (1858) Conch. Icon., Pinna Pt. 10, fig. 18.
The shell is elongate fan-shaped, somewhat keeled down the middle, with
a median sulcus and with a variable number of hollow, tubular spines.
The shell substance is thin and fragile, ranging in color from almost brick-red
to light pink. In some cases, the spines are absent, and it is this smooth
form that has received the name carnea.
Length 220, height 85, width 29 mm.
Porto Rico: Mayaguez; Caja de Muertos Is.
Virgin Islands: St. Thomas; Tortola.
Genus ATRINA Gray
Alrina Gray (1847) Proc. Zool. Soc. London, Pt. 15: 190.
TYPE (by original designation), Pinna nigra Chemnitz.
The shell is large, thin, elongate trigonal to triangular, and gaping at the
posterior end. The umbones are terminal. The sculpture consists of
longitudinal ridges, smooth or ornamented with spines. The hinge is
edentulous.
SCIENTIFIC SURVEY OF PORTO RICO
Atrina rigida (Dillwyn)
PLATE 3, FIGURE 4
Pinna rigida Dillwyn (1817) Catal. 1: 327.
Pinna subviridis Reeve (1858) Pinna PI. 17, fig. 32.
The shell is similar to the preceding species in general appearance, but
ranges in color from light-horn-color to dark brown. There is no keel or
sulcus running down the middle of the shell.
Length 150, height 72, width 33 mm.
Porto Rico: Mayaguez.
Virgin Islands: St. Thomas.
Family PTERIIDAE
The shell is aviculoid, bialate, monomyarian and inequivalve, with an
alivincular ligament. The byssus issues from a notch in the smaller valve.
The ventricle is ventral to the rectum, with anterior and posterior aortas.
The gills are filamentary or imperfectly reticulate, with direct and reflected
laminae attached to the mantle, but the tips behind the adductor floating
free. The foot is subcylindrical, small and grooved. The anal end of the
rectum is free and erectile. The young are dimyarian and sometimes
pass through a distinct nepionic stage.
KEY TO THE GENERA OF PTERIIDAE
(1) Posterior auricle elongate. .Pteria
(1') Posterior auricle not elongate. ............. Pinciada
Genus PTERIA Scopoli
Pieria Scopoli (1777) Introduct. lHist. Nat. Lap. Plant. Anim. Naturae: 397.
TYPE (by monotypy), Mytilus hirundo Linnaeus.
The shell is of varying size, nacreous with the posterior and anterior ends
auriculate. The posterior auricle is elongate. The anterior margin below
the auricle is insinuated by a narrow byssal gape. The sculpture is weak.
The hinge area is narrow, almost as long as the dorsal margin of the valves.
The right and left valves bear 1 or 2 small denticles fitting into shallow
sockets, and a long posterior lateral lamella.
Pteria colymbus (Rdding)
PLATE 3, FIGURE 8
Pinctada colymbus Rdling (1798) Museum Boltenianum, 2: 166.
Avicula atlantica Lamarck (1819) Anim. s. Vert. 6: 148.
The elongate posterior wing and oblique form of the shell characterize
this species in the Antillean region. It is often dark brown or almost black
in color. The interior is pearly.
Length 89, height 59, width 25 mm.
Porto Rico: Ponce.
Virgin Islands: St. Croix; Tortola; Virgin Gorda.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Genus PINCTADA Rdding
Pinctada Roding (1798) Museum Holtenianum 2: 166.
.llargoritiphora Mtgerle (1811) Ges. Nat. Fr. Berlin Mag. 5: 66.
Margaritifera Schumacher (1816) Overs. K. Dansk. Vid. Selsk. Forhandl. 7 (ex. Humphrey).
TYPE (by subsequent designation, Iredale, 1915), lMyilus margaritiferus Gmelin.
The shell is of varying size, nacreous with the posterior and anterior ends
auriculate. The posterior auricle is not elongate. The byssal gape is on
the right valve below the small triangular auricle. The sculpture consists
of lamellations of the surface at the growth lines, often forming tongue-like
projections which may be arranged in radial rows. The hinge is similar to
that in Pieria.
Pinctada radiata (Leach)
PLATE 3, FIGURE 7
A. icula radiala Leach (1814) Zool. Miscell. 1:98, Pl. 43.
This is the small pearl oyster of the West Indies. It is often beautifully
mottled with yellow and varying shades of brown. Some individuals show
a remarkable sculpture of lamellations of the surface at the growth lines.
The lamellae curl up and overlap one another, giving a very bizarre appear-
ance to the shell.
Length 75, height 72, width 28 mm.
Porto Rico: Mayaguez; Boca Prieta; Point Brea.
Virgin Islands: St. Thomas; St. Johns; Tortola.
Family ISOGNOMONIDAE
The shell is submytiliform with a broad posterior wing. It is mono-
myarian, the anterior adductor being absent in the adult. It is also inequi-
valve and edentulous, with a serial, multivincular ligament. Species usually
byssiferous, with a moderate gape or none. The gills are reticulate and
united to each other and to the mantle. The anatomy otherwise is gen-
erally as in the Pteriidae.
Genus ISOGNOMON Solander
Isognomon Solander (1786) Cat. Portland Mus.: 41.
Melina Retzius (1788) Diss. Nova. Test. Gen.: 22.
Perna Bruguibre (1789) Enc. Meth. (Vers), 1 (1): 13 (not Retzius, 1788).
Isognomon Riding (1799), Mus. Bolten. 2: 168.
Isognomon Link (1807) Beschr. Nat. Samml. Univ. Rostock, (3): 155.
TYPE (by autonomyy, Ostrea isognomon Linnaeus.
The shell reaches a large size and is obliquely subquadrate, with the poste-
rior end auriculate or rounded and the anterior margin insinuated by a nar-
row byssal gape near the dorsal margin. The ligament area bears numerous
parallel grooves perpendicular to the dorsal margin of the valves. The
interior is nacreous centrally.
KEY TO THE SPECIES OF Isognomon
(1) Ligament pits relatively widely spaced, color light. ..I. listeria
(1') Ligament pits relatively close-set, color dark ...................... (2)
SCIENTIFIC SURVEY OF PORTO RICO
(2) Shell smooth internally .. ... .... I. alata
(2') Body portion of shell usually distinctly delimited from the marginal portion by a
ridge. I. vulsella
Isognomon alata (Gmelin)
PLATE 4, FIGURE 3
Ostrea alata Gmelin (1792) Syst. Nat. (Ed. 13): 3339.
Perna ephippium Reeve (1858) Conch. Icon. 11: Pl. 2, fig. 8.
This species is large and spatulate and is not easily confused with any
other in the region. It is usually dark in color. The units of the multi-
vincular ligament are relatively close-set.
Length 80, height 80, width 8 mm.
Porto Rico: San Juan; Mayaguez; Guanica; Parguera; Puerto Real; En-
senada Honda, Culebra.
Virgin Islands: St. Thomas.
Isognomon listerl (Hanley)
PLATE 3, FIGURE 6
Perna vulsella Lamarck (1818) Anim. s. VerL 6: 141 (var. b).
Perna lisleri Hanley (1846) III. Cat. Biv. Shells: 259.
Perna lamarckeana d'Orbigny (1846) Moll. Cubana 2: 360.
This species is lighter in color than the other two and is usually charac-
teristically marked with rusty red. The markings are radial fan-shaped
rays. The ligamental pits are relatively more widely spaced as well.
Length 25, height 60, width 7 mm.
Porto Rico: Mayaguez; Ponce; Guanica; Hucares; Arroyo; Talleboa;
Puerto Real; Ensenada Honda, Culebra.
Virgin Islands: St. Thomas.
Isognomon vulsella (Lamarck)
PLATE 4, FIGURES 1 AND 2
Perna velsella Lamarck (1818) Anim. s. Vert. 6: 141.
Perna bicolar C. B. Adams (1845) Proc. Boston Soc. Nat. Hist. 2: 9.
Perna chemnitziana d'Orbigny (1846) Moll. Cubana 2: 359.
The shell substance is dark, and the ligamental pits are relatively close-
set. The most characteristic feature of this species is the raised pallial line
which marks off the body portion of the shell from the distal portion.
Length 28, height 18, width 7 mm.
Porto Rico: San Juan; Ponce; Guanica; Caja de Muertos Is.
Virgin Islands: St. Thomas.
Superfamily OSTRACEA
In this group, the shell is inequivalve, sessile, and extremely varied in
form, even within a single species. It is, apparently, particularly sus-
ceptible to ecological conditions in this respect. The valves fit together
very closely. The epidermis is inconspicuous. The outer layer of the
shell is prismatic, and the inner is subnacreous or porcellaneous. The hinge
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
area extends on each side of the beaks, with the ligament in the form of a
broad band, running from beak to beak. The dentition is obsolete, although
some species have a series of small denticles along the margin, especially
near the hinge area. The pallial line is simple and often quite obscure.
The anterior adductor muscle is absent. There is no byssus.
Family OSTREIDAE
The shell is spatulate or rounded and distorted by early adherence to
other objects. It is dimyarian when young, with the anterior adductor
absent or very much reduced in the adult. The hinge is edentulous or with
obscure, schizodont dentition. The foot is rudimentary or absent. The
species are monoecious or dioecious, and the position of the ventricle varies.
Genus OSTREA
Ostrea Linnaeus (1758) Syst. Nat. (Ed. 10): 696.
TYPE (by subsequent designation, Children, 1823), Ostrea edulis Linnaeus.
The characters for Ostrea are the same as those listed above for the
Ostreidae, since this genus alone constitutes the family in the recent fauna.
This genus is subdivided into two groups by the presence or absence of a
promyal chamber and the associated position of the adductor muscle scar.
KEY TO THE SUBGENERA OF Oslrea
(1) Promyal chamber absent, muscle scar subcentral. ...........Ostrea s.s.
(1') Promyal chamber present, muscle scar distally located.......... Crassostrea
Subgenus OSTREA s.s.
There are two recognized sections of this subgenus in this fauna.
KEY TO THE SECTIONS or Ostrea s.s.
(1) Valve margins straight or irregularly folded; right valve flatter and smoother
than left valve. ........... ... .. .Ostreas.s.
(1') Valves similarly sculptured, with sharp radial plications and corresponding folds
in the margins ..... ........ Lopha
Ostrea (Ostrea) cristata Born
PLATE 4, FIGURES 8 AND 9
Osirea crislala Born (1778) Index Mus. Caes. Vind.: 98.
Ostrea equestris Say (1834) Am. Conch. (6), PI. 58 (in part).
Ostrea sprela d'Orbigny (1846) Voy. Amer. Merid. (Moll.): 672.
Ostreafundala Holmes (1858) Post Plioc. Foss. S. Carolina 11: PI. 2,fig. 10.
This is a small, rather circular species, with a centrally located muscle
scar. It has an irregularly folded interlocking margin. The beaks are
slightly curved. The inner margins of the valves bear a row of denticles
on each side of the hinge that extend about one-third of the distance to the
opposite side of the valves. The bottom figure on Say's plate is probably
a broad specimen of 0. frons. The others are 0. cristata.
Length 39, height 36, width 11 mm.
Porto Rico: Gallardo Bank; Ponce.
SCIENTIFIC SURVEY OF PORTO RICO
Section LOPHA R6ding
Lopha Roding (1798) Mus. Bolten. 2: 168.
Aleclryonia Fischer (1807) Mus. Demid. 3: 269.
Dendrostraea Swainson (1840) Treat. Malacol.: 389.
Dendrostrea Agassiz (1846) Nomen. Zool. Index Univ.
Rastellum Fischer (1886) Man. de Conchyl.: 926.
Ostrea (Ostrea) frons (Linnaeus)
PLATE 4, FIGURES 4 AND 7
.Ilylilus frons Linnaeus (1758) Syst. Nat. (Ed. 10): 704.
Ostrea ruballa Lamarck (1819) Anim. s. Vert. 6 (1): 210.
Osirea limacella Lamarck (1819) Anim. s. Vert. 6 (I):
The radial plicate sculpture and corresponding sharply folded valve mar-
gins are typical of this species. The inner margins are closely dotted with
minute, pimply denticles for nearly their whole circumference. The muscle
scar is located well up toward the hinge. The beaks are somewhat curved.
Internally the shell substance is translucent white, while the outside is
usually a purplish red. The animal is frequently found attached to the
stem of a gorgonian by a series of clasping projections from the shell. Often,
too, there is a longitudinal ridge running down the center of the shell in
these forms. This ridge has even been given taxonomic importance by
some writers. It is nothing more than a reflection of the gorgonian stem
to which the animal is attached.
Length 30, height 54, width 19 mm.
Porto Rico: San Juan; Ponce; E. of Cayo Caribe.
Virgin Islands: St. Thomas; St. Croix; St. Johns; Tortola; Virgin Gorda
Subgenus CRASSOSTREA Sacco
Crassoslrea Sacco (1897), [in] Sacco and Bellardi, tMoll. Terr. Terz. Piemonte e Liguri
TYPE (by original designation), Ostrea tirginica Gmelin.
These species have the right valve decidedly smaller than the left. The
beaks are elongate and strongly oblique. The inner margin is smooth.
The adductor muscle is located well down toward the distal border, and
there is a promyal chamber.
KEY TO THE SPECIES OF SUBGENUS Crassostrea
(1) Attached valve not greatly larger than free valve, margins not heavily shaded
with purple, muscle scar frequently purple .0. virginica
(1') Attached valve much larger than free valve, margin with considerable deep
purple coloration. .0. rhisophorae
Ostrea (Crassostrea) virginica Gmelin
PLATE 4, FIGURE 5
Ostrea clongala Solander (1786) Cat. Portland Mus 55, not Born (1780).
Ostrea virginica Gmelin (1792) Syst. Nat. (Ed. 1.): 3336.
Ostrea brasiliana Lamarck (1819) Anim. s. Vert. 6 (I): 205.
Ostrea borealis Lamarck (1819) ibid.: 207.
Ostrea canadensis Lamarck (1819) ibid.: 207.
Ostrca semicylindrica Say (1822) Jour. Acad. Nat. Sci. Phila. (1) 2: 228.
Ostrea virginiana Sowerhy (1822) Genera of Shells, fig. 2.
Osirea triangularis Ilolmrs (1856) Proc. Elliott Soc. 1: 29.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Ostrea sirginiajn procyon Holmes (1858) Post. Plioc. Foss. South Carolina: 10, Pl. 2,fig. 9a.
Ostreafloridensis Sowerby (1871) [in] Reeve, Conch. Icon. 18 pL. 29, fig. 76 a-b.
This is an extremely variable form, running from oval to elongate in
shape. The margins are straight, or slightly folded, and entirely smooth
right up to the hinge. The muscle scar is distally located and usually
colored a deep purple. There is a promyal chamber. The beaks are long
and quite strongly curved.
Length 66, height 122, width 29 mm.
Porto Rico: Ponce; Mayaguez; Guanica; Puerto Real; Ensenada Honda,
Culebra.
Virgin Islands: St. Croix.
Ostrea (Crassostrea) rhizophorae Guilding
PLATE 4, FIGURE 6
Osirca rhi:ophorae Guilding (1828) Zool. J. 3 (12):
Ostrea brasiliana of authors, not Lamarck.
Ostrea parasilica of authors, not Gmelin.
This is typically a deep-cupped form, with a flat upper valve, very much
discrepant in size, and fitting well down into the lower valve. The inner
margins are straight and smooth. The beaks are twisted dorsally. The
muscle scar is well down toward the margin, indicating that there probably
is a promyal chamber.
On first inspection of the left valve, the muscle scar appears to be nearly
centrally located, but this is due to the discrepancy in size between the left
and right valves. If the right, or free, valve is examined, it will be seen
that the scar is distally located, allowing plenty of room for a promyal
chamber. There is usually considerable purple coloration, especially around
the margin of the left, or attached, valve. The surfaces of both upper and
lower valve are typically smoother than in the preceding species.
Length 46, height 70, width 18 mm.
Porto Rico: San Juan; Ponce.
Virgin Islands: St. Thomas; St. Croix.
Suborder ISODONTA
The fundamental dentition is taxodont but this becomes obsolete in the
adult, and its function is taken over by modifications of the auricular crura
which form interlocking processes. There is an internal resilium. Typi-
cally, in the left valve, there is a socket, and then outside of that a tooth on
each side of the resilium. There are corresponding teeth and sockets in the
right valve. These teeth and sockets are modifications of certain ridges
which strengthen the auricles in many species of Peclen and which Dall
named crura. This type of hinge, then, must be regarded as a remarkable
specialization of certain features of the shell, themselves the result of modi-
fications of the valves initiated through influence of external sculpture, but
morphologically distinct from the structures which in other bivalves we call
teeth.
There are two superfamilies in this suborder.
SCIENTIFIC SURVEY OF PORTO RICO
KEY TO THE SUPERFAMILIES OF ISODONTA
(1) Shell fan-shaped, with more or less well-developed ears..... .Pectinacea
(1') Shell rounded, without wings or ears... .Anomiacea
Superfamily PECTINACEA
The shell is usually inequivalve and fan-shaped with more or less well
developed wings or ears as they are called in the group. The epidermis is
generally inconspicuous. The type of shell substance is quite diverse in
the different species. It is typically subnacreous internally, but the outer
layers may be tubuliferous or more rarely prismatic. The hinge area,
when present, extends on both sides of the beaks. The ligament consists
of a band, often much thickened, which runs from beak to beak across the
hinge line. The normal dentition of the hinge is obsolete, and its functions
are performed, if at all, by modifications of the ears, which form interlocking
processes. These auricular crura, as they are called, are thickened ridges
on the inner surfaces of the ears, which become highly developed and re-
semble true teeth. They have one very noticeable difference, however, in
that they fit together concentrically and not alternately. This concentric
dentition is found only in the Pectinacea and their close relatives, the
Anomiacea. The pallial line is simple. The anterior adductor muscle is
absent. A byssus is sometimes present but is usually poorly developed.
There are three families of the Pectinacea in this region.
KEY TO THE FAMILIES OF PECTINACEA
(1) Shell sessile, isodont hinge teeth strongly developed.. .Spondylidae
(1') Shell not sessile, or, if so, dentition weak. .(2)
(2) Shell shape fundamentally subcircular.. .Pectinidae
(2') Shell shape obliquely ovate.... Limidae
Family PECTINIDAE
The shell is inequivalve, inequilateral, auriculate, usually closed, mono-
myarian, and usually free. The area is amphidetic or obscure. The liga-
ment is obsolete externally, the immersed portion forming an internal
resilium. The hinge teeth are taxodont in the very young, obsolete later
with the auricular crura sometimes developed into a feeble isodont dentition.
The byssus is not strongly developed and frequently absent in the adult.
The soft parts are generally similar to those of the Spondylidae.
KEY TO THE GENERA OF PECTINIDAE
(1) Shell with internal radial lirae. Amusium
(1') Shell without internal lirae. .(2)
(2) Ears subequal, one or both valves strongly inflated .Pecten
(2') Anterior ears larger than posterior ones, both valves moderately inflated...
Chlamys
Genus PECTEN Mtiller
Pecten MQller (1776) Zoolog. Danicae Prodr.: 248.
TYPE (by subsequent designation. Schmidt, 1818). Osirea maxima Linnaeus
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
The shell is subequilateral, inequivalve, the right valve being larger and
more inflated. The ears are subequal, the dorsal margin of those of the
right valve recurving downward over the hinge line. The pallial line is
simple.
KEY TO THE SUBGENERA OF Peclen
(1) Right valve strongly inflated, left valve flat..........................Euvola
(1') Both valves strongly inflated. ...................... Plagioctenium
Subgenus EUVOLA Dall
Evola Dal], 1898, Trans. Wagner Free Inst. Sci. 3 (4): 694.
TYPE (by original designation), Ostrea siczac Linnaeus.
The right valve is extremely inflated. The surface is polished, the ribs
being moderate or obsolete and without radial striation. The concentric
sculpture is inconspicuous. The left valve may be with or without con-
spicuous radial and concentric sculpture; it may be flat or concave.
KEY TO THE SPECIES OF SUBGENUS Euvola
(1) Ribs flattened, interspaces narrow ............P. ziczac
(1') Ribs rounded, interspaces nearly as wide as the ribs................. P. raveneli
Pecten (Euvola) ziczac (Linnaeus)
PLATE 5, FIGURE 1
Ostrea ziczac Linnaeus (1758) Syst. Nat. (Ed. 10):
The flat valve is typically reddish or purple in color, sometimes light
brown. The lower valve is deeply cupped and light in color. The ribs are
flattened, and the surface is polished. Dall's record of P. laurenti Gmelin
is probably based on a dark specimen of P. ziczac.
Length 100, height 90, width 26 mm.
Porto Rico: Mayaguez; Ponce.
Virgin Islands: St. Thomas.
Pecten (Euvola) raveneli Dall
PLATE 5, FIGURE 2
Pecten medius of authors, not Gmelin.
Pecten hemicyclica of authors, not Ravenel.
Pecten raveneli Dall, 1898, Trans. Wagner Free Inst. Sci., : 721, Pl. 29, fig. 10.
This species differs from the preceding in having more pronounced ribbing
on both upper and lower valves. The coloration is much the same.
Length 50, height 47, width 13 mm.
Porto Rico: Mayaguez.
Virgin Islands: St. Thomas.
Subgenus PLAGIOCTENIUM Dall
Plagioclenium Dall (1898) Trans. Wagner Free Inst. 3 (4): 696.
TYPE (by original designation), Peclen ventricosus Sowerby, = Peclen circularis Sowerby.
Both valves strongly convex; ribbing strong and regular. The right
valve is somewhat more inflated than the left. The ctenolium is frequently
obsolete in the adult stage.
SCIENTIFIC SURVEY OF PORTO RICO
Pecten (Plagioctenium) gibbus (Linnaeus)
PLATE 5, FIGcURE 4
Osirea gibba Linnaeus (1758) Syst. Nat. (Ed. 10): 698.
This is a common species on the east coast of the United States and is
occasionally found in the West Indies. It is a tumid species with strong,
rounded ribs. The right valve is frequently light in color, and the left one
is variously colored, sometimes brightly colored.
Length 30, height 28, width 19 mm.
Porto Rico: San Juan; Arecibo; Aguadilla.
Virgin Islands: St. Thomas.
Pecten (Plagioctenium) gibbus mayaguezensis Dall and Simpson
PLATE 5, FIGURE 3
Pecten mayaguezensis Dall and Simpson (1901) Bull. U. S. Fish Comm. 20: 465, Pl. 5, figs. 7-0.
? Ostrea nucleus Born (1780) Text Mus. Caes. Vind.: 107, P. 7, fig. 2.
This species is very similar to P gibbus but runs smaller in size. It has
much the same color varieties as that species. It ranges from southern
Florida to northern South America. Dall regarded it as distinct and it
may be a dwarf variety of true gibbus. At the present time its status is not
definitely established, but it may be that this is the form represented by
the name nucleus Born.
Length 21, height 19, width 8.5 mm.
Porto Rico: Mayaguez; Ponce.
Virgin Islands: St. Thomas.
Genus CHLAMYS Rbding
Chlamys R6ding (1798) Mus. Bolten. 2: 161.
TYPE (by subsequent designation, Dall, 1898), Pecten islandicus Muller.
The shell is inequilateral and nearly equivalve, the right valve being
slightly more flattened than the left. The radial ribs are numerous and
often increased in number by intercalation. They are usually imbricated
by the concentric sculpture. The anterior ears are larger than the posterior
ones. The right anterior ear is notched for the passage of a byssus. The
margin below this notch is pectinated, often with a well-developed cteno-
lium.
KEY TO THE SUBGENERA OF Chlamys
(1) Sculpture feeble or absent, shells thin and fragile. .Palliolum
(1') Sculpture strong, shells relatively solid (2)
(2) Ribs numerous and dichotomously branching Chlamys s.s.
(2') Ribs few in number, large, not branching. Lyropecten
Subgenus CHLAMYS s.s.
The characters are those of the generic diagnosis but with the limiting
features included in the key.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
KEY TO THE SPECIES OF Chlamys s.s.
(1) Scales on the ribs very close-set. (2)
(1') Scales on the ribs high and widely spaced .C. imbricata
(2) Valves moderately inflated. .C. muscosa
(2') Valves compressed. (3)
(3) Radial ribs moderately heavy, about 20 in number C. ornata
(3') Radial ribs very fine, numbering more than forty .C. multisquamala
Chlamys (Chlamys) Imbricata (Gmelin)
PLATE 5, FIGURE 7
Ostrea imbricalus Gmelin (1792) Syst. Nat. (Ed. 13); 3318.
Peclen lemniscalus Reeve: Dall and Simpson (1901) Bull. U. S. Fish Comm., 20: 466.
This beautiful species is not likely to be confounded with any other in the
West Indian region. The high vaulted scales are very characteristic.
The shell is white and variously mottled and spotted with red or brown.
Length 27, height 31, width 6 mm.
Porto Rico: San Juan.
Virgin Islands: St. Thomas.
Chlamys (Chlamys) ornata (Lamarck)
PLATE 5, FIGURE 6
Pecten ornatus Lamarck (1819) Anim. s. Vert. 6: 176.
The name ornata is a good one for this colorful little species. The shell
color is white and it is beautifully mottled with dark red. The ribs are
close-set and delicately scaled.
Length 20, height 23, width 8 mm.
Porto Rico: Mayaguez; Guanica; Cayo Caribe.
Virgin Islands: St. Thomas.
Chlamys (Chlamys) muscosa (Wood)
PLATE 5, FIGURE 5
Osirea muscosa Wood (1828) Suppl. Index Test.: 47.
Pecten exasperalus of authors, not Sowerby.
This species is found in a variety of colors ranging from lemon yellow
through many shades of red to light and dark brown. It is variously
mottled and clouded. In those specimens which have lived in a sheltered
spot or are covered with a growth of sponge the scales on the ribs are often
strongly developed, lending a cellular appearance to the surface. Animals
from a more exposed place have only the low imbricate bases of these scales
left.
Length 37, height 38, width 17 mm.
Porto Rico: San Juan.
Virgin Islands: St. Thomas.
Chlamys (Chlamys) multisquamata (Dunker)
PLATE 6, FIGURE 2
Pecten multisquamaius Dunker (1864) Mala. Blatt. 11: 100.
Pecten multisquamatus Dunker, Novitates Conchol.: 67, PI. 24, figs.
SCIENTIFIC SURVEY OF PORTO RICO
The many fine threadlike ribs will easily separate this species from the
others. The lower valve is light-colored, while the upper one may be rusty
red or fawn colored.
Length 49, height 54, width 10 mm.
Virgin Islands: St. Croix.
Subgenus LYROPECTEN Conrad
Lyropecten Conrad (1862) Proc. Acad. Nat. Sci. Phila.: 291.
TYPE (by subsequent designation, Dall, 1898), Lyropeclen esirellanus Conrad.
The shell is equilateral, somewhat inequivalve, and with heavy radial ribs.
The left valve is slightly more inflated than the right. The ribs are rela-
tively few in number and do not branch dichotomously. They are orna-
mented with minute radial striation.
Chlamys (Lyropecten) antillarum (Recluz)
PLATE 6, FIGURE 6
Peclen anlillarum Recluz (1853) Jour. de Conchyl., 4: 53, Pl. 5, fig. 1.
This is one of the smallest of the Lyropectens. There are about ten
large ribs. The fine radial striations are well marked. The lower valve is
light-colored. The upper one is light on the umbonal area, becoming orange
or red distally. The colored portion is often banded concentrically with
white. The submargins are frequently striped diagonally with fine white
lines.
Length 23, height 24, width 17 mm.
Porto Rico: San Juan.
Virgin Islands: St. Thomas.
Section NODIPECTEN Dall
Nodipeclen Dall (1898) Trans. Wagner Free Inst. Sci., 3 (4): 695.
Type (by original designation), Osirea nodosa Linnaeus.
The ribs are intermittently nodose, with more or less prominent hollow
nodes or bullae. The imbricate surface layer is sometimes very marked.
Chlamys (Lyropecten) nodosa (Linnaeus)
PLATE 6, FIGURE 1
Ostrea nodosa Linnaeus (1758) Syst. Nat., Ed. 10: 697.
The strong ribs with heavy nodes characterize this species. The radial
striation is very prominent. Typically the shell is dark red, but an occa-
sional specimen is found that is bright orange.
Length 145, height 140, width 38 mm.
Porto Rico: Mayaguez; Ponce.
Virgin Islands: St. Thomas; Tortola; Caneel Bay and Flannagans Passage,
St. John.
Subgenus PALLIOLUM Monterosato
Palliolum Monterosato (1884) Nomen. Gen. Spec. Conch. Medit., p. 5.
Pseudamusium of authors not Mdrch (1853).
TYPE (by subsequent designation, Cossman and Peyrot, 1912), Pecten lestae Bivona.
McLEAN: BIIALVE MOLLUSKS OF PORTO RICO
The valves are much compressed, thin, and more or less translucent.
The sculpture is feeble or absent. The inner surfaces of the valves are
smooth.
Chlamys (Palliolum) nana (Verrill and Bush)
PLATE 6, FIGURE 3
Cyclopectcn nanus Verrill and Bush (1897) Trans. Conn. Acad. Sci., 10: 85, 92, P1. 16, figs. 12-12c.
This is a deep-water form, but specimens were obtained near Mayaguez,
and it is included here to avoid confusion in case more specimens are found
in relatively shallow water. It is very small, nearly orbicular, and much
compressed. The valves appear smooth, but there are some fine concentric
striae and minute radial riblets. The interior is smooth. It is semitrans-
parent whitish or horny, often clouded or irregularly rayed with milky
white.
Length 5.5, height 5.5, width 1.7 mm.
Porto Rico: Mayaguez.
Genus AMUSIUM Rbding
Amusium Rbding, 1798, Mus. Bolten., 2: 165.
TYPE (by subsequent designation, Herrmannsen, 1846), Ostrea pleuronecies Linnaeus.
The valves are subcircular and very thin. In many the outer edge of the
right valve is not completely calcified and bends over the left. The outer
surface of the valves may have slight radial or concentric sculpture, but
the inner surface has radial lirae which are characteristic of the genus. In
those species which have color the lower or right valve is frequently white,
or sometimes tinted with yellow, while the upper or left valve is red.
KEY TO THE SPECIES OF AMUSIUM
(1) Left valve with very minute concentric sculpture, ears relatively small, internal
lirae not usually reaching beyond the middle of the shell. .A. dalli
(1') Left valve with well-developed concentric sculpture, ears relatively large, in-
ternal lirae reaching almost to margin of shell. .A. pourtalesianum
Amusium dalli E. A. Smith
PLATE 6, FIGURE 4
Amusium dalli E. A. Smith (1886) Challenger Lamell., p. 308, PI. 22, figs.
The valves are equilateral and nearly equivalve, the right one slightly
more convex than the left; they are very thin and fragile. The ears are
small and subequal. The right valve is practically smooth, while the left
valve has very fine concentric ridges. There are seven to ten, pointed,
internal lirae. The color is translucent milky white with sometimes a
brownish shading on the disk.
Length 59, height 62, width 6 mm.
Porto Rico: off the south coast.
Amusium pourtalesianum Dall
PLATE 6, FIGURE 5
Amusium pourialesianum Dall (1886) Bull. Mus. Comp. Zool., 12: 211, PI. 4. fig. 3. PI. 5, fig. 12.
SCIENTIFIC SURVEY OF PORTO RICO
The valves are small, thin, compressed and subcircular. The right
valve is slightly more convex than the left. The ears are small and nearly
even, but are larger in proportion than in the preceding species. The right
valve appears smooth but has microscopic concentric ridges and radial
riblets. The left valve has well-developed concentric ridges. There are
nine to eleven somewhat club-shaped internal lirae. The color is trans-
lucent milky white, sometimes suffused with brown or rusty red.
Length 13, height 13, width 2.5 mm.
Porto Rico: Mayaguez.
Family SPONDYLIDAE
The shell is inequivalve, nearly equilateral, closed, pectiniform, obscurely
auriculated, monomyarian, and sessile. The area is amphidetic and much
larger on the attached valve. The ligament is alivincular with the resilium
more or less submerged. The byssus is obsolete. The armature of the
hinge is originally taxodont but obsolete in the adult and replaced by the
typically isodont development of the auricular crura. The gills are fili-
branchiate with a reflected limb. The foot is small, subcylindrical, with a
terminal funicle. The ventricle embraces the rectum with the auricles
intercommunicating below it. There is an anterior and a posterior aorta.
The mantle lobes are free, without siphons, usually with an internally pro-
jecting lamina or curtain near the margin at right angles to the plane of
the valves. The anal end of the rectum is usually free for a short distance.
KEY TO THE GENERA OF SPONDYLIDAE
(1) Radial ribs few and strong; cardinal area of right valve not very broad. Plicatula
(1') Radial ribs numerous, usually relatively fine; cardinal area of right valve very
broad. .Spondylus
Genus SPONDYLUS Linnaeus
Spondylus Linnaeus (1758) Syst. Nat., Ed. 10: 690.
TYPE (by subsequent designation, Gray, 1847), Spondylus gaederopus Linnaeus.
The shell reaches a large size and is trigonal-suborbicular with the auricles
small and subequal. The right valve is higher and more inflated than the
left. The sculpture consists of low radial ribs and foliaceous lamellae or
spines. The cardinal area is wider on the right valve than on the left.
The chondrophore is small, triangular, and median. The hinge of both
valves consists of two heavy crural teeth, representing laterals, and two
sockets symmetrically placed with respect to the chondrophore; the right
valve bears along the lower outer edge of the cardinal area, on both sides, a
rude horizontal lamella fitting into the space between the crural tooth and
the lower margin of the cardinal area of the left valve. The muscular
impressions are suborbicular, posterior.
Spondylus americanus Hermann
PLATE 7, FIGURE
Spondylus americanus Hermann (17811 Der Naturforscher, Halle, 16: 51.
Osirea eehinalus Martyn (1784) Univ. Conchol., fig. 154 (not binomiall.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Spondylus dominicensis Roding (1798) Mus. Bolten., p. 193.
Spondylus americanus Hermann: HFedley and Pilsbry (1912) Nautilus 26: 46.
Spondylus dominicensis Roding: Fulton (1937) Nautilus 51: 38.
As far as I have been able to tell, this is the only species of the genus in
the West Indian region. It exhibits a very wide range of variation both in
color and in sculpture. In his Tertiary Fauna of Florida (1898, p. 759),
Dall gives an extensive synonomy. I have checked many of these names,
and it seems that there is only one species represented. It seems to be
very responsive to environmental conditions and perhaps genetically un-
stable as well.
Length 80, height 90, width 40 mm.
Porto Rico: Mayaguez; Ponce; Boca Prieta; Punta Melones; Caja de
Muertos.
Virgin Islands: St. Thomas; Flannagans Passage, St. John; Tortola;
Virgin Gorda.
Genus PLICATULA Lamarck
Plicatula Lamarck (1801) Syst. des. Anim. s. Vert., p. 152.
TYPE (by subsequent designation, Gray, 1847), Plicalula gibbosa Lamarck.
The shell is small, irregular in outline, and attached by either valve. The
sculpture consists of broad radial ribs that may divide near the margin.
The cardinal area is very small with the chondrophore narrow, elongate,
and flanked on each side by a fluted crural tooth representing a lateral, and
also by a socket. The impression of the adductor muscle is ovate and
posterior. The margins of the valves are fluted.
Plicatula gibbosa Lamarck
PLATE 6, FIGURE 7
Plicalula gibbosa Lamarck (1801) Syst. des. Anim. s Vert., p. 132.
Plicatula ramosa Lamarck (1819) Anim. s. Vert., p. 184.
Plicalula vexillara Guppy (1874) Geol. Mag. 1: 444, Pl. 17, fig. 7.
This flat, trigonal species with its heavy radial ribs, sometimes dichoto-
mously branching distally, is not easily confused with any other in the
recent fauna. It is usually light-colored and marked with red. Occasional
specimens are somewhat shaded with brown.
Length 25, height 25, width 10 mm.
Porto Rico: Aguadilla; Cayo Caribe.
Virgin Islands: St. Thomas.
Family LIMIDAE
The shell is thin, equivalve, auriculate, gaping, pectiniform, and mono-
myarian. The shell substance is fibrous, with minute tubules, not nacreous
or prismatic. The hinge is edentulous or has traces of taxodont armature.
The area is amphidetic and equal in both valves. The ligament is alivincu-
lar with the resilium subinternal. The gills are filibranchiate, with direct
and reflected laminae. The mantle lobes are free with a curtain as found
in the Spondylidae. The foot is small, digitiform, and grooved. The
SCIENTIFIC SURVEY OF PORTO RICO
species are usually byssiferous, the byssus passing through the gape of the
valves. The anal end of the rectum is free and erectile.
KEY TO THE GENERA OF LIMIDAE
(1) Valves gaping, shell inequilateral. .Lima
(1') Valves closed, shell equilateral. .Limatula
Genus LIMA Cuvier
Lima Cuvier (1798) Tabl. Elem. list. Nat. Anim., p. 421.
TYPE (by monotype), Ostrea lima Linnaeus.
The shell is medium-sized, moderately inflated, obliquely inequilateral,
with the anterior submargin flattened, and the anterior and posterior ends
narrowly gaping. The auricles are unequal, the posterior one larger. The
sculpture consists of scaly ribs. The cardinal area is wide, triangular, with
the chondrophore large and central and the hinge edentulous. The ad-
ductor scar is high and posterior. The margins of the valves are fluted.
KEY TO THE SUBGENERA OF LIMA
(1) Submargins impressed ...... .... ............... (2)
(1') Submargins not impressed. .................... Manteilun
(2) Radial sculpture straight. .Lima s.s.
(2') Radial sculpture divaricate... Clenoides
Subgenus LIMA s.s.
This is the typical group of Limas with strong, straight radial ribs. The
ribs are often strongly spinose.
Lima (Lima) lima (Linnaeus)
PLATE 7, FIGURE 3
Ostrea lima Linnaeus (1758) Syst. Nat. Ed. 10: 699.
Lima squamosa Lamarck (1801) Syst. Anim. s. Vert., p. 136.
The shell is broadly fan-shaped with regular rows of vaulted spines. The
periostracum is inconspicuous, and the shell substance white.
Length 45, height 55, width 22 mm.
Porto Rico: Mayaguez; Guanica; Mona Island.
Virgin Islands: St. Thomas; St. Johns; Tortola; Virgin Gorda.
Subgenus CTENOIDES M6rch
Clenoides Mdrch (1853) Catal. Yoldi, 2: 56.
TYPE Lima scabra Born.
The radial sculpture is divaricate, with a line of divergence running from
the umbos more or less centrally to the distal margin. There is a brownish
periostracum. The shell substance is white.
KEY TO THE SPECIES OF CTENOIDES
(1) Radial sculpture coarse ......... L. scabra
(1') Radial sculpture fine........................ .... ............ L. tlenera
McLEAX: BIV'ALI'E MOLLUSKS OF PORTO RICO
Lima (Ctenoides) scabra (Born)
PLATE 7, FIGURE 2
Ostrea scabra Born, 1780, Test. Mus. 110.
The coarse radial sculpture and the brown periostracum will identify
this species.
Length 45, height 55, width 17 mm.
Porto Rico: Mayaguez; Ponce; Aguadilla; Guanica; Caja de Muertos
Is.; Ensenada Honda, Culebra.
Virgin Islands: St. Thomas; St. Johns; Tortola; Virgin Gorda.
Lima (Ctenoides) tenera Sowerby
PLATE 7, FIGURE 4
Limi lenera Sowerby, 1846, Thes. Conch. p. 84, PL. 21, figs. 10-11.
The radial sculpture is very fine, and the periostracum is of a light fawn-
color.
Length 40, height 54, width 17 mm.
Porto Rico: Mayaguez; Ponce; Parguera, Margarita Pass.
Virgin Islands: St. Thomas; Caneel Bay, St. Johns; Tortola; Virgin
Gorda.
Subgenus MANTELLUM Rdding
Mantellum Roding, 1798, Mus. Bolten., 2: 160.
Limaria Link, 1807, Beschr. Nat. Samml. Univ. Rostock (3). 157.
TYPE (by subsequent designation, Bucquoy, Dautzenberg and Dollfus, 1888), Osirea inflata Gmeli
The shell is thin, inflated and obliquely inequilateral, the posterior and
anterior ends gaping, and the submargins not impressed. The auricles are
small and subequal. The sculpture consists of narrow radial ribs, rough-
ened by incrementals. The cardinal area is narrow, the chondrophore very
large. Part of the shell under the cardinal area is excavated on the poste-
rior side. The hinge is edentulous. The ventral margins of the valves are
weakly fluted.
KEY TO THE SPECIES OF MANTELLUM
(1) Shell inflated, excavation under posterior cardinal area small. .L. inflata
(1') Shell relatively compressed, excavation under posterior cardinal area large. ..
L. hians
Lima (Mantellum) inflata (Gmelin)
PLATE 7, FIGURE 5
Ostrea inflala Gmelin (1792) Syst. Nat., Ed. 13: 3321.
Lima inflata Lamarck (1819) Anim. s. Vert., 6: 156.
Lima fasciata Sowerby (1872) Icon., 18, PI. 4, fig. 17.
Lima pellucida C. B. Adams, 1846, Proc. Boston Soc. Nat. Hist., 2: 102.
Both this species and the following are very fragile, delicately sculptured
shells. They are thin and translucent white. The surface is ornamented
with fine threadlike radial ribs. Inflata is rather tumid and less gaping
than hians. The excavation under the posterior cardinal area is not so
SCIENTIFIC SURVEY OF PORTO RICO
pronounced as in hians. In large specimens the height relative to the
length is less than in hians.
Length 10, height 16, width 8 mm.
Porto Rico: Mayaguez; Ensenada Honda, Culebra.
Lima (Mantellum) hians (Gmelin)
PLATE 7, FIGURE 6
Ostrea hiA nt Gmelin (1792) Syst. Nat., Ed. 13: 3332.
Lima Jragillis Sowerby, 1872, Conch. Icon., 18, Pl. 4, fig. 18.
This species is similar to the preceding but somewhat more slender and
spatulate, especially in large specimens. The excavation under the poste-
rior cardinal area is large. It cuts back sharply under the hinge line leaving
the posterior part of the hinge projecting like a hook or tooth. The valves
are relatively compressed. The sculpture is usually less pronounced than
in inflata.
Length 12, height 20, width 7 mm.
Porto Rico: Aguadilla.
Virgin Islands: St. Thomas; St. Croix; Tortola.
Genus LIMATULA Wood
Limalula Wood (1839) Mag. Nat. Hist. (n.s.) 3: 235.
TYPE (by subsequent designation, Gray, 1947), Pecten subauriculata Montagu.
The shell is equivalve and nearly equilateral, valves inflated and not
gaping. The sculpture consists of clear-cut nodular radial ribs. The sub-
margins are not impressed. Internally the margins are fluted. The hinge
area is nearly symmetrical, and the chondrophore is broad and triangular.
Limatula subauriculata (Montagu)
PLATE 7, FIGURE 7
Prcten subauriculata Montagu (1808) Test. Brit., Suppl., p. 63, PI. 29, fig.
This symmetrical little species exhibits almost none of the obliquity that
is typical of most of the Limidae. The radial ribs are quite straight and
are ornamented with regular rounded beading. The shell color is white.
Length 6, height 8.5, width 6 mm.
Porto Rico: Mayaguez.
Superfamily ANOMIACEA
Some of the Anomiacea are free-living and some are sessile. As in other
groups, the free-living species have the shell much more regular in form than
the sessile ones. There are no wings or ears on the shells in this group.
The shell is thin, and the epidermis is inconspicuous. Under this, there are
traces of a simple prismatic layer, then tubuliferous material, and finally a
nacreous lining. The hinge area is obscure, usually small, and extending
on both sides of the beaks. The ligament is divided into an obscure outer
portion or true ligament, extending on each side of the beaks, and an internal
resilium, set down into the hinge plate below the beaks. This condition is
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
similar to that found in some of the more highly developed Teleodesmacea.
The hinge is edentulous or, if teeth are present, they are of the unusual
concentric type found in the Pectinacea. The pallial line is obscure. The
anterior adductor muscle is absent. There is a byssus which in some forms
may become modified to a horny or calcified plug.
Family ANOMIIDAE
The shell is variable. When sessile, it is irregular and inequivalve. The
species are byssiferous when young. In most of the genera the byssus be-
comes modified to a calcified or horny plug passing through a foramen in
the attached valve and fastened to other bodies-a condition which may be
permanent or transient. The area is small, amphidetic. The ligament is
amphidetic, more or less internal, and supplemented by an internal resilium,
for which the auricular crura serve as chondrophores. It is alivincular or
multivincular. The hinge is usually edentulous, rarely rugose with amor-
phous interlocking rugosities. The posterior adductor is small, subcentral
and in the sessile forms reinforced by the pedo-byssal muscles, which are
modified to serve as adductors.
KEY TO THE GENERA OF ANOMIIDAE
(1) Left valve of shell bearing four muscular impressions.. .Anomia
(1') Left valve of shell bearing two muscular impressions. .Pododesmus
Genus ANOMIA Linnaeus
Anomia Linnaeus (1758) Syst. Nat., Ed. 10: 700.
TYPE (by subsequent designation, Gray, 1847). Anomia ephippium Linnaeus.
The right or attached valve is flat with a large sinus on its upper border,
through which the pluglike byssus passes. The right valve bears a single
muscular impression. The left valve is entire, convex; it has a ligamental
fossette below the summit and bears four muscular impressions.
Anomia simplex d'Orbigny
PLATE 8, FIGURE 2
Anomia simplex d'Orbigny (1846) Moll. Cubana, 2: 367, PI. 38, figs. 31-33.
Anomia ephippium of authors, not Linnaeus.
The shell is irregular, fitting and often imitating the object to which it is
attached, suborbicular, thin and semitransparent. The interior of the
valves is nacreous and shining. The exterior has concentric scaly ridges.
The color is whitish, silvery, greenish straw, or pale brownish.
Length 35, height 35, width 7 mm.
Porto Rico: Mayaguez; Ponce.
Virgin Islands: St. Thomas; Tortola.
Genus PODODESMUS Philippi
Pododesmus Philippi (1837) Arch. f. Naturg., 3 (1): 385.
TYPEn (by monotypy), Pododesmus decipiens Philippi = P. rudis Broderip.
This genus is similar in characteristics to Anomia, except that the left
valve bears only two muscular impressions.
SCIENTIFIC SURVEY OF PORTO RICO
Pododesmus rudis (Broderip)
PLATE 8, FIGURE I
Placunanomia rudis Broderip (1834) Proc. Zool. Soc. London, 2 (13): 2.
Pododesmus decipiens Philippi (1837) Arch. f. Naturg., 3 (1): 386.
The shell is very irregular, compressed, suborbicular, oval, oblong or
somewhat elongate, moderately solid. The lower valve is normally flatter
than the upper. The byssal opening is round, oval, or closed in old speci-
mens. The surface is ornamented with fine, irregular, broken ridges crossed
by scaly or foliaceous growthlines. The interior is shining, the lower valve
generally having a brown blotch in its center. The color is whitish or
greenish.
Length 40, height 40, width 6 mm.
Porto Rico: San Juan; Aguadilla; Punta Melones.
Virgin Islands: St. Thomas.
Suborder DYSODONTA
The shell substance is largely subnacreous, rarely more or less prismatic.
The shell is equivalve, very inequilateral; the anterior end is much reduced,
and the umbones are strongly prosogyrous. There are no wings. The
hinge is edentulous or provided with teeth which are derived from the ex-
ternal sculpture where it impinges on the hinge margin. The curved dental
processes or dysodont teeth are fundamentally a continuation of the internal
ribs, which alternate with the external ribs in primitive bivalves. The
hinge area extends on both sides of the beaks and is often obscure. The
ligament is parivincular. There are two adductor muscles, but the anterior
one exhibits a varying degree of reduction. The pallial line is usually
simple, although in a few rare cases it is sinuate. There is generally a func-
tional byssus in the adult.
Family MYTILIDAE
The shell is equivalve, very inequilateral, heteromyarian, and very slightly
gaping. It is typically dysodont or edentulous; with the ligament usually
external, deep-seated; rarely with an alivincular, internal resilium. The
pallial line is simple. The ventricle has an anterior aorta. The gills are
attached distally and dorsally, usually with a reflected limb to the filaments.
The mantle lobes are united below the anal siphon, otherwise free.
KEY TO THE GENERA OF MYTILIDAE
(1) Hinge line without teeth or crenulations. .2
(1') Hinge line with teeth or crenulations. .3
(2) Umbones anterior but not terminal. Modiolus
(2) Umbones terminal Lilhophaga
(3) Shell mytiliform, pointed anteriorly and broadly ,atulate posteriorly
Braclvdonltes
(3') Shell not mytiliform, broadly rounded anteriorly .4
(4) Shell rounded subcquadrate, length usually greater than altitude, radial sculpture
interrupted in the middle of the shell by a smooth area showing only growth
lines .................... ............ ................. M odiolaria
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
(4') Shell ovate, altitude usually greater than length, radial sculpture continuous over
surface of shell. .Crenella
Genus MODIOLUS Lamarck
.Ilodiolus Lamarck (1799) Mem. Soc. Hist. Nat. Paris, p. 87.
TYPE (by monotypy), Mytilus modiolus Linnaeus.
The shell is oblong or elongate, oblique, generally inflated toward the
anterior end and compressed posteriorly. The surface is smooth or con-
centrically striated, seldom ribbed although in some species feebly striated
on the posterior slope. The umbones are obtuse, anterior, but not ter-
minal. The anterior margin is expanded in front of the umbones but quite
smooth. The hinge line is without teeth or crenulations. The anterior
adductor muscle scar is small. Posterior muscle and byssal scars are united,
the former rounded and the latter long and narrow.
KEY TO THE SUBGENERA OF MODIOLUS
(1) Shells moderate to large in size, not extremely thin, moderately inflated, surface
usually with concentric growth lines. .Modiolus s.s
(1') Shells small, very thin, compressed, smooth and polished. Amygdalum
Subgenus MODIOLUS s.s.
The characters are as listed in the generic description, with the limiting
features of the key.
There are two species of this subgenus in this fauna.
KEY TO THE SPECIES OF MODIOLUS S.S.
(1) Shell large, produced, and rather pointed anteriorly .M'. tulipa
(1') Shell small, bluntly rounded anteriorly .M. castaneus
Modiolus (Modlolus) tullpa Lamarck
PLATE 8, FIGURE 4
Modiola tulipa Lamarck (1819) Anim. s. Vert.,
This species is common throughout the upper Antillean region and is well
known. It frequently has rays of red color running out from the umbones
to the margin. The periostracum is heavy and characteristically dark
chestnut in color.
Length 85, height 40, width 40 mm.
Porto Rico: San Juan; Mayaguez; Playa Humacao; Caja de Muertos Is.-
Boca Prieta.
Virgin Islands: St. Thomas; St. Johns; Tortola.
Modiolus (Modiolus) castaneus Say
PLATE 8, FIGURE 6
Modiola caslanea Say (1822) Jour. Acad. Nat. Sci. Phila., 2: 266.
Modiola lignea Reeve (1858) Conch. icon., 10, PI. 10, fig, 71.
This species has been placed in different genera by various authors. It is
frequently found referred to the genus Bolula. Dall placed it in section
SCIENTIFIC SURVEY OF PORTO RICO
Lioberus under the genus Modiolaria. Jukes-Browne has it under Modiolus
as originally described. On the basis of shell characters there seem to be
no grounds for removing it from the genus in which Say placed it. Ana-
tomical studies may provide such grounds, but until they are made and
published it would appear necessary to leave it here. The shape is much
like that of tulipa but it is more quadrate and is more rounded at the anterior
end. It is a smaller species, seldom exceeding 28 millimeters in length.
The surface shows concentric growth lines, and the epidermis is chestnut-
colored and polished. There is frequently an accumulation of byssal
threads forming a sort of sheath over the posterior ends of the valves.
Length 28, height 15, width 14 mm.
Virgin Islands: St. Thomas.
Subgenus AMYGDALUM Megerle
Amygdalum Megerle (1811) Mag. Ges. Naturf. Freunde Berli
TYPE (by monotypy), Amygdalum dendriticum Megerle.
The shell is generally similar to Modiolus s.s., but more compressed, the
surface being smooth and polished and the epidermis glossy and not hirsute.
Modiolus (Amygdalum) dendriticus (Megerle)
PLATE 8, FIGURE 7
Amygdalum dendriticum Megerle (1811) Mag. Ges. Naturf. Fr. Berlin,
.lytilus arborescens Dillwyn (1817) Cat. Shells, 1: 306.
Iodiola papyria Conrad (1846) Proc. Acad. Nat. Sci. Phila.,
This species is thin and fragile, compressed, and with a greenish or yellow-
ish, glossy epidermis.
Length 34, height 12, width 7 mm.
Porto Rico: San Juan; Mayaguez.
Genus LITHOPHAGA Riding
Lithophaga Rbding (1798) Mus. Bolten., 2: 156.
Lilhodomus Cuvier (1817) Regn. Anim., 2: 471.
TYPE (by monotypy), Lithophaga myluloides Roding = IMytilus lithophagus Gmelin.
The shell is generally long, narrow, and subcylindrical. The umbones
are at the anterior end, which is rounded and inflated. The posterior end
is generally wedge-shaped, but sometimes cylindrical and tapering. The
surface is smooth or wrinkled. The hinge line is straight without crenula-
tions. The margins are quite smooth. The adductor scars are oval and
nearly equal, with the byssal scars oval and small. These animals are
typically burrowing forms.
KEY TO THIE SUBGENERA OF LITHOPHAGA
Shell elongate, narrow, subcylindrical, and rounded anteriorly with the umbones
not prominent Lithophaga s.s.
(1') Shell oblong, subrhomboidal, squared anteriorly with the umbones prominent
and spirally curved ................... ...................... Botula
McLEAN: BII'ALVE MOLLUSKS OF PORTO RICO
Subgenus LITHOPHAGA s.s.
The characters are as given for the genus, with the limiting features of
the key. Two sections used by Dall are outlined in the text.
KEY TO THE SPECIES OF LITIIOPHAGA S.S.
(1) Epidermis light brown, adult about 90 mm. long. .L. antillarum
(1') Epidermis chestnut, adult about 50 mm. long. .L. nigra
Lithophaga (Lithophaga) antillarum (d'Orbigny)
PLATE 8, FIGURE 9
Lithodomus antillarum d'Orbigny (1846) Moll. Cubana, 2: 332, PI. 28, figs. 12, 13.
Modiola corrugate Philippi (1846) Abbild. u. Beschr., 2: 147, pl. 1, fig. 1.
This large, cigar-shaped species is much lighter in color than the following
one. It is light brown. The surface is wrinkled with fine diagonal striae,
which are divaricate on the posterior end.
Length 86, height 26, width 20 mm.
Porto Rico: Guanica; Puerto Real; Arroyo.
Virgin Islands: St. Thomas.
Lithophaga (Lithophaga) nigra (d'Orbigny).
PLATE 8, FIGURE 8
Lithodomus niger d'Orbigny (1846) Moll. Cubana, 2: 351, PI. 28, figs. 10, 11.
Modiola caribaeo Philippi (1847) Abbild. u. Beschr., 3: 20, Pl. 2, fig. 5.
Modiola antillarum Philippi (1847) op. cil., fig. 4.
This species is smaller and much darker in color than the preceding.
The diagonal striae are seldom present on the posterior part of the shell,
although some specimens have faint indications of them there. They are
well marked on the central part of the shell.
Length 33, height 18, width 17 mm.
Porto Rico: Guanica.
Virgin Islands: St. Thomas; Tortola.
Section DIBERUS Dall, 1898
The shell is similar to that of Lithophaga, but the animal has the habit of
depositing a calcareous crust on the exterior of the valves. This crust
bears two or more radial sulci extending backward from the beaks. The
incrustation is plumelike, arranged in a distinct pattern on the areas be-
tween the sulci, and when projecting beyond the ends of the valves, opposed
symmetrically, not alternate and twisted.
Lithophaga (Lithophaga) bisulcata (d'Orbigny)
PLATE 9, FIGURE 3
Lithodomus bisulcata d'Orbigny (1846) Moll. Cubana, 2: 133, Pl. 28, figs. 14-16.
Modiola appendiculala Philippi (1846) Abbild. u. Beschr., 2: 150 PIl. 1, fig. 4.
Lithodomus biexcavatus Reeve (1857) Conch. Icon., 10, Pl. 4, fig. 22a-b.
The calcareous crust on this species is characteristic. Superficially it
has the appearance of being soft and chalky but it is quite hard. Over
SCIENTIFIC SURVEY OF PORTO RICO
most of the shell it is densely pustulose, but posteriorly, in the area of the
sulci, it is laminar and pseudocellular. The dark chestnut color of the
shell is visible around the margin or in areas where the crust has broken off.
Length 57, height 17, width 15 mm.
Porto Rico: Guanica; Puerto Real; Arroyo.
Virgin Islands: St. Thomas.
Section MYOFORCEPS Fischer, 1886
Shell as in Lithophaga, but the animal deposits a calcareous crust on the
exterior surface of the valves. This crust is smooth and projects in a
twisted process from the posterior end of each valve.
Lithophaga (Lithophaga) arlstata (Dillwyn)
PLATE 9, FIGURE 1
Mytilus arislalus Dillwyn (1817) Cat. Shells, 1: 303.
Modiola caudigera Lamarck (1819) Anim. s. Vert., 6: 116.
Lilhodomus forficatus Ravenel (1861) Proc. Acad. Nat. Sci. Phila., p. 44.
This species differs from the preceding in that the calcareous crust is
smooth over the whole surface and the extensions beyond the posterior end
of the shell are twisted. The process of the right valve overlaps that of the
left. The true color of the shell itself is lighter, too, being light brown where
it is exposed around the borders of the valves.
Length 43, height 12, width 12 mm.
Virgin Islands: St. Thomas.
Subgenus BOTULA Ma rch
Botula Miirch, 1853, Cat. Yoldi, 2: 55.
TYPE (by subsequent designation, Dall, .11oliota cinnamomea Lamarck.
The shell is oblong, subrhomboid; the umbones are terminal, prominent,
and spirally curved.
KEY TO THE SPECIES OF BOTULA
Surface relatively smooth, growth lines not heavily impressed, adult shells about
40 mm. or more in length .L. cinnamomea
(1') Surface furrowed with heavily impressed periodic growth lines, adult shells about
20 mm. in length .L. fusca
Lithophaga (Botula) cinnamomea (Lamarck)
PLATE 8, FIGURE 5
iola cinnamomea Lamarck (1819) Anim. s. Vert., 6:
There has been a certain amount of confusion between this species and
the next one. They seem to be distinct. Both were founded on West
Indian material. Gmelin cites a figure in Lister which is marked as repre-
senting a Jamaican shell. Lamarck gives Mauritius as a locality in his
description, but refers to a figure of a West Indian specimen in the Con-
chylien Cabinet. The relationship between the present species and similar
species from the Indo-Pacific region is still uncertain. Many burrowing
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
species are apparently widespread in their distribution. At present it is
not possible to tell whether apparently conspecific populations in different
zoological provinces are genetically the same or only morphologically so
because of similar habits and environment. L. cinnamomea is a larger shell
than fusca. The surface is relatively smooth. If an area in the umbonal
region of cinnamomea the size of a full grown fusca be compared with a
specimen of that species, this difference is clear.
Length 45, height 21, width 20 mm.
Virgin Islands: St. Thomas.
Lithophaga (Botula) fusca (Gmelin)
PLATE 8, FIGURE 3
Mytilus fuscus Gmelin (1792) Syst. Nat., Ed. 13: 3339.
This species is considerably smaller than the preceding and has strongly
impressed periodic growth lines, giving the valves a concentrically sulcate
appearance. The umbones are relatively more prominent.
Length 19, height 8, width 9 mm.
Virgin Islands: St. Thomas; St. Croix.
Genus BRACHYDONTES Swainson
Brachydontes Swainson (1840) Malac., p. 384.
TYPE (by monotypy), .lModiola sulcata Lamarck (1819) = Mytilus citrinus Rdding, not Modiolus sulcatus
Lamarck (1807).
The shell is generally finely ribbed, but sometimes wrinkled, or even
smooth. The anterior development of the shell, and consequently the
position of the umbones, is variable. The hinge line is generally straight
and terminates in an angle posteriorly. The ligament is rather short and
marginal or inframarginal. The anterior margin is typically provided with
several close-set teeth. The posterior border is crenulated, sometimes
throughout its length, above and behind the ligament, sometimes only
behind the ligament. The muscle scars are similar to those of Modiolus.
KEY TO THE SUBGENERA OF BRACHYDONTES
(1) Umbones subterminal. .Brachydonles s.s
(1') Umbones terminal 2
(2) Anterior adductor muscle present. .Hormomya
(2') Anterior adductor muscle absent. .Ischadium
Subgenus BRACH YDONTES s.s.
The characters are as given for the genus, with the limiting features of
the key.
Brachydontes (Brachydontes) citrinus (Roding)
PLATE 9, FIGURE 2
.l ytifus citrinus Roding (1798) ?Mus. Bolten., p. 157.
Modiola sulcala Lamarck (1819) Anim. s. Vert., 6: 113; not *I. sulcata Lamarck (1807).
Mylilus cubitus Say (1822) Jour. Acad. Nat. Sci. Phila., 2: 263.
SCIENTIFIC SURVEY OF PORTO RICO
This species is quite distinct. It has a conspicuous yellow epidermis,
sometimes tinged with green. The shell substance is often blotched irregu-
larly with reddish or brownish coloration. The crenulations are heavily
impressed along the entire hinge margin.
Length 46, height 17, width 13 mm.
Virgin Islands: St. Thomas; St. Johns.
Subgenus HORMOMYA March
Ilormomya Mdrch (1853) Cat. Yoldi, 2: 53.
TYPE (by monotypy), My:itus exustus Linnaeus.
The shell is finely ribbed. The umbones are virtually terminal, possibly
just slightly subterminal. The anterior side of the shell is straight or in-
curved.
Brachydontes (Hormomya) exustus (Linnaeus)
PLATE 9, FIGURE 4
3Mylilus exuslus Linnaeus (1758) Syst. Nat., Ed. 10: 705.
Mytilus domingensis Lamarck (1819) Anim. s. Vert., 6: 121.
The shell is finely striate, with the striae dichotomously branching. The
epidermis is fuscous to dark brown. Internally the shell is shaded with
purplish brown. The marginal crenulations are obscure above the ligament,
but well marked posterior to it.
Length 37, height 20, width 11 mm.
Porto Rico: San Juan; Mayaguez; Ponce; Guanica; Pt. San Geronimo;
Hucares; Puerto Real; Ensenada Honda, Culebra.
Virgin Islands: St. Thomas.
Subgenus ISCHADIUM Jukes-Brown
Ischadium Jukes-Brown (1905) Proc. Mal. Soc. London, 6 (4): 223.
TYPE (by monotypy), Mytilus hamalus Say, My/ilus recurvus Rafinesque.
The shell is oblong or pyriform in outline, sculptured all over with strong,
raised, divaricating ribs. The umbones are slightly divergent. The ante-
rior riblets are well marked and correspond with a variable number of dyso-
dont teeth. The ligament is long and without crenulations behind it in the
adult. The anterior adductor scar is absent, and the anterior byssal scar is
very small, while the posterior byssal scar is large and broadly united to
that of the posterior adductor.
Brachydontes (Ischadium) recurvus (Rafinesque)
PLATE 9, FIGURE 5
Mylilus recurrus Rafinesque (1820) Coq. Biv, Ohio, p. 55.
Mytilus hamatus Say (1822) Jour. Acad. Nat. Sci. Phila., 2: 265.
The epidermis is heavy and dark greenish or brownish color. The shell
substance is shaded with blue externally and appears brownish-purple on
the interior except for the internal margin which is white.
Length 50, height 25, width 20 mm.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Porto Rico: San Juan;'Ensenada Honda, Culebra, and Sail Rock between
Culebra and St. Thomas.
Virgin Islands: St. Thomas.
Genus MODIOLARIA Beck
Modiolaria Beck (1840) [in] E. Robert, Roy. Recher. Gr6nl. Pl. 1, figs. 1-4.
TYPE (by subsequent designation, Stoliczka, 1871), Mylilus discors Linnaeus.
The shell is rhomboidal and sculptured by two groups of striae, which
radiate from the beaks, leaving the middle portion of the shell smooth.
The umbones are incurved. The hinge is edentulous or crenulated, and the
hinge plate is finely notched.
KEY TO THE SUBGENERA OF MODIOLARIA
Shell rounded or obtusely angulate posteriorly, epidermis not particularly hirsute
Mfodiolaria s.s.
(1') Shell attenuate, acutely angular posteriorly, epidermis hirsute on the dorsal
posterior area... Gregariella
Subgenus MODIOLARIA s.s.
The characters are those given for the genus, with the limiting features
of the key.
Modlolaria lateralis (Say)
PLATE 9, FIGURE 7
Aylilus laleralis Say (1822) Jour. Acad. Nat. Sci. Phila., : 264.
The shell is ovate-rhomboidal. About the central one-third of the surface
is smooth. The anterior striate area is slightly smaller than the posterior
one. The umbones are full and inflated, and umbonal ridge is strong, run-
ning obliquely back to the posterior ventral margin. The epidermis is
greenish or brownish horn color.
Length 6, height 3.5, width 3 mm.
Porto Rico: San Juan; Mayaguez; Guanica; Pt. Brea; Vieques.
Virgin Islands: St. Thomas.
Subgenus GREGARIELLA Monterosato
Gregariella Monterosato (1884) Nom. Conch. Medit., p. 11.
Bolulina Dall (1898) Bull. U. S. Nat. Mus., 37: 38.
TYPE (by subsequent designation, Dall, 1898), Modiolus petagnae Scacchi.
The shell is attenuate posteriorly and sharply angled at the tip. The
umbonal ridge is strongly developed. The smooth unstriated central area
is smaller than in typical Modiolaria and is located relatively farther for-
ward. The epidermis is hirsute posteriorly.
Modiolaria (Gregariella) coralliophaga (Gmelin)
PLATE 9, FIGURE 8
Mylilus coralliophagus Gmelin (1792) Syst. Nat., Ed. : 3359.
Hfodiola semen Lamarck (1819) Anim. s. Vert., 6: 115.
Modiola divaricala Philippi (1847) Zeitschr. f. Mala., p. 115.
SCIENTIFIC SURVEY OF PORTO RICO
This species is rather streamlined in appearance, being blunt and rounded
anteriorly and tapering off to a point at the posterior end. The epidermis
is tan to brown and hirsute, particularly above the sloping umbonal ridge
on the posterior dorsal area.
Length 17, height 7, width 7 mm.
Porto Rico: Mayaguez.
Virgin Islands: St. Thomas.
Genus CRENELLA Brown
Crentella Brown (1827) Ill. Conch. Gt. Brit., PIl. 31, figs. 12-14.
TYPE (by monotypy), Mytilus decussatus Montagu.
The shell is oval or rhomboidal. The surface is ornamented with longi-
tudinal and concentric striae. The umbones are incurved. The hinge
margin is denticulate. The denticles appear as formed where the external
sculpture impinges on the margin. When only one denticle is present, it is
crenulate.
Crenella divaricata (d'Orbigny)
PLATE 9, FIGURE 6
Nuculocardia divaricala d'Orbigny (1846) MIoll. Cubana, 2: PIl. 27, figs. 56-59.
The shell is very small, the height being greater than the length. The
surface is sculptured with radial divaricating ribs, which maybe very slightly
nodular. The shell color is white. The epidermis is inconspicuous. The
hinge of this animal presents, superficially, a remarkable analogy to a teleo-
desmacean hinge. The denticles in the umbonal region are large and grouped
in a manner suggesting cardinal teeth, while there is another group posterior
to the ligament which is strongly developed. The hinge margin is enlarged
in the region of this latter group and gives the impression of a lateral tooth
as found typically in the teleodesmacean hinge.
Length 3, height 3.5, width 3 mm.
Porto Rico: Mayaguez.
Order ANOMALODESMACEA
This group is closer to the Teleodesmacea than it is to the preceding order.
It is probable that the two groups had a common general origin while the
Prionodesmacea followed a separate line of descent. Part of the original
stock has produced the perfected types of Pelecypods which have lost all
their archaic characters and have become the Teleodesmacea, while another
part has come down to us as the Anomalodesmacea retaining indications of
their primitive characters, probably on account of the burrowing habit
which has shielded them from many vicissitudes and checked in this way
the perfecting processes of selection. The group is not unspecialized.
Many of their archaic characters are veiled by later adaptations, but they
do appear to indicate types which probably were ancestral to some of the
modern, more highly developed bivalves.
Major phylogenies which have followed separate lines of descent are not
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
apparent in this order. For this reason it has not been divided into sub-
orders. Groups of families which seem to be closely related have been
brought together under the headings of superfamilies. The Porto Rican
fauna includes two of these.
KEY TO THE SUPERFAMILIES OF ANOMALODESMACEA
(1) Gills V-shaped, reticulate. .Laternulacea
(1') Gills foliobranchiate or lamellar, slightly or not at all reticulate, frequently de-
generate or absent. ......... Poromyacea
Superfamily LATERNULACEA
The gills are reticulate and V-shaped. The ventricle embraces the
rectum and usually bears an anterior and a posterior aorta. The animal
does not secrete a calcareous tube external to the shell. The ligament may
be with or without a lithodesma.
There is only one family of this group represented in the Porto Rican
fauna.
Family LYONSIIDAE
The shell is inequivalve, thin, subnacreous and edentulous. The liga-
ment is obsolete and the resilium internal, uniting the edges of a long,
mesial lithodesma to a narrow, chondrophoric, submarginal ridge on each
valve. The beaks are entire, and the valves are almost closed. The
pallial sinus is distinct. The gills are folded, united and septary behind
attached to the dome of the mantle and to the siphonal septum. The foot
is compressed, grooved, and byssiferous, without an opisthopodium. There
is an opisthopodial orifice. The pedal orifice is small. The siphons are
short, separate, and papillose. The branchial one has the valve incon-
spicuous.
Genus LYONSIA Turton
Lyonsia Turton (1822) Conch. Insul. Brit., 17: 34.
Type (by monotypy), Mya striata Montagu (1822) = Mya norvegica Gmelin (1792).
The description for the genus is much the same as given for the family.
There is a fine radial sculpture, and the periostracum often has bits of
adherent sand. The length of the shell is greater than the height, and it is
truncate behind. The hinge is edentulous with a ligament in a sulcus, and
a large lithodesma. The pallial sinus is obscure and angular.
Lyonsia beana d'Orbigny
PLATE 9, FIGURE 9
Lyonsia beana d'Orbigny (1846) Moll. Cubana, 2: 225, PI. 25, figs. 26-28.
The shell is small, thin and polished. It is very inequilateral, gaping
both anteriorly and posteriorly, the anterior end is short and attenuated,
and the posterior end laterally compressed.
This species is found living commensally with sponges and compound
SCIENTIFIC SURVEY OF PORTO RICO
ascidians; this indicates one reason for its very irregular shape. The
epidermis is often brownish, and the shell sometimes tinted with purple.
Length 27, height 14, width 11 mm.
Porto Rico: Vieques.
Virgin Islands: St. Thomas.
Superfamily POROMYACEA
The gills are foliobranchiate or lamellar, slightly or not at all reticulated,
and frequently degenerate or even absent. The lamellae when fully de-
veloped are attached to one another by interlocking giant cilia, disposed in
bands or patches, and by occasional connective fibers which are not of a
vascular nature. Often there is a special development of the branchiosi-
phonal septum. The valves are free. The mantle lobes are united and
have developed siphons and a pedal, but not opisthopodial opening. The
resilium is reinforced below by a lithodesma.
There are two families represented in this fauna.
KEY TO THE FAMILIES OF POROMYACEA
(1) Shell rostrate, rarely with surface granulation. .Cuspidariidae
(1') Shell not rostrate, the surface granulose.. Verticordiidae
Family CUSPIDARIIDAE
The shell is subequivalve and rostrate, rarely with surface granulations.
The shell substance is earthy or cellulocrystaline. The hinge is edentulous
or with subumbonal desmodont tuberculations, and is sometimes buttressed.
The ligament is subinternal, anterior to the beaks or obsolete. The re-
silium is internal, with a mesial or ventral lithodesma. The area is am-
phidetic or obscure. The valves are closed except at the tip of the rostrum.
The pallial line is simple, and the retraction of the siphons usually is ef-
fected by the contraction of the septum, which leaves a scar on the valves
resembling a pallial sinus. The ventricle is bilobate, embracing the rectum
or dorsal to it, with two aortas. The gills are obsolete or absent, repre-
sented only by the ciliated foramina in a muscular septum. The palps
are degenerate or obsolete. The foot is small, digitiform, and grooved, with
a minute byssus but not opisthopodium. The siphons are united, long or
short, with a few papillae and an obsolete curtain valve.
Genus CUSPIDARIA Nardo
Cuspidaria Nardo (1840) Revue Zool., p. 30.
TYPE (by subsequent designation, Hermannsen (1846) Tellina cuspidata Olivi.
The shell is rostrate and concentrically sculptured. The hinge has a
small, posteriorly inclined chondrophore in each valve and an elongate
ridge behind it. The ligament, when present, is always anterior to the
beaks.
KEY TO THE SUBGENERA OF CUSPIDARIA
(1) Valves smooth or concentrically sculptured,..
(1') Valves radially sculptured ....... .
Cuspidaria s.s.
..... . . . . . Cardiomya
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Subgenus CUSPIDARIA
The valves are smooth or feebly concentrically sculptured. The fossette
of the resilium is posteriorly inclined and attached to the hinge-margin by
its posterior edge. There is one posterior lateral tooth in the right valve.
The siphons are elongate.
Cuspidaria (Cuspidaria) obesa (Lov&n)
PLATE 10, FIGURE 1
Neaera obesa Lovin (1846) Ind. Moll. Scand., p. 48.
The surface is rather smooth, with low, concentric sculpture. It is
rostrate posteriorly but not so much so as in specimens of Cardiomya.
The umbones are full, and the shell is tumid.
Length 13 mm.
Porto Rico: Mayaguez.
Subgenus CARDIOMYA A. Adams
Cardiomya A. Adams (1846) Ann. Mag. Nat. Hist. (3), 13: 330.
TYPE (by monotypy), Neaera gouldiana Hinds
The valves are sculptured radially, and the fossette of the resilium is more
vertical and prominent. Otherwise it is similar to Cuspidaria s.s.
KEY TO THE SPECIES OF CARDIOMYA
(1) Rostrum long and narrow .C. perrostrata
(1') Rostrum short and obtuse. .2
(2) Radial ribs few, prominent. .C. ornalissima
(2') Radial ribs numerous, less prominent. C. costellata
Cuspidaria (Cardiomya) perrostrata Dall
PLATE 10, FIGURE 2
Cuspidaria perrostrata Dall (1881) Bull. Mus. Comp. Zool., 9: 296, PIl. 2, figs. 3a 3b.
This is an elegant little species, as are all the members of this subgenus.
It has about twenty radial ribs on the disk of the shell and five or six delicate
riblets on the rostrate posterior portion. The ribs are very clearly incised.
The ribs on the central part of the disk alternate in size, every other one
being slightly larger than the intervening one.
Length 5 mm.
Porto Rico: Mayaguez.
Cuspidaria (Cardiomya) costellata (Deshayes)
PLATE 10, FIGURE 3
Corbula costellata Deshayes (1837) Explor. Sci. More, Geol., p. 86, PIl. 7, figs. 1-3.
Sphena alternata d'Orbigny (1846) Moll. Cubana, 2: 286, PI. 27, figs. 17-20.
The rostrum is shorter and more obtuse in this species than in the pre-
ceding one. There are about 25 ribs on the main body of the shell which
alternate in size on the disk, as in the preceding species. The rostrum has
SCIENTIFIC SURVEY OF PORTO RICO
one well-marked rib, which is probably in the nature of an umbonal ridge,
and several very fine riblets.
Length 4 mm.
Porto Rico: Mayaguez.
Cuspidaria (Cardlomya) ornatissima (d'Orbigny)
PLATE 10, FIGURE 4
Sphena ornatissima d'Orbigny (1846) Moll Cubana, 2: 286, PI. 27, figs. 13-16.
Neaera costaia Bush (1885) Trans. Conn. Acad., 6 (2): 472, P1. 45, fig. 21.
This species is quite distinctive in the presence of seven to nine sharp,
prominent ribs with broad concave interspaces. The rostrum is variable,
sometimes being short and truncate and in other specimens moderately
long. In this species, as in the preceding, the ribs tend to alternate in size.
Length 6 mm.
Porto Rico: Mayaguez.
Virgin Islands: St. Thomas.
Family VERTICORIIDAE
The shell is subequivalve, nacreous, and cellulocrystaline. It is granulose
externally. The hinge bears a strong tubercle in the right valve before
the resilium, and the dorsal margins are modified to overlie and underlie
each other. The ligament is obsolete, and the resilium opisthodetic and
internal, with a strong ventral lithodesma. The area is obscure or absent,
but there is a depressed false lunule before the beaks. The valves are
closed, and the pallial sinus is shallow and obscure. The ventricle embraces
the rectum and probably has two aortas. The gills are foliobranchiate,
simple, and without a lateral reflected extension. They are adnate on
the anteriorly extended, fleshy, imperforate siphonal septum. The palps
are obsolete. The foot is digitiform, not byssiferous, and without an
opisthopodium. The pedal foramen is small, and the siphons short, sepa-
rate, and papillose. The branchial siphon is without a conspicuous valve.
Genus VERTICORDIA J. Sowerby
Verficordia J. Sowerby (1844) Min. Conch. Gt. Britain, 7 (112): 67.
TYPE (by monotypy), Verlicordia cardliformis J. Sowerby.
The shell is equivalve, usually small, and suborbicular. Its substance is
pearly. The umbones are subcentral or anterior, prominent, prosogyrous,
and often strongly involute. There is a deeply impressed false lunule.
The sculpture consists of strong radial ribs. The ligament is submarginal.
The resilium is supported by a lithodesma. There is usually a strong
cardinal tooth in the right valve and sometimes in the left, although the
left valve is typically devoid of true teeth. Occasionally a posterior lateral
tooth is developed, but more often the valve margins are modified to func-
tion as laterals. The adductor muscle scars are small and often obscure.
The pallial line is simple or feebly waved. The ventral margins of the
valves are deeply fluted.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Vertlcordia ornata (d'Orbigny)
PLATE 10, FIGURE 5
Trignnulina ornata d'Orbigny (1846) Moll. Cubana, 2: 292, PI. 27, figs. 30-33.
This beautiful little species is quadrate in outline and moderately inflated.
It has nine or ten prominent radial ribs with broad, smooth, concave inter-
spaces. The posterior third of the shell is relatively smooth.
Length 3 mm.
Porto Rico: Mayaguez.
ORDER TELEODESMACEA
This order is made up of forms which are presumably the most perfected,
although not always the most specialized, of bivalve mollusks. It probably
had one general origin with the Anomalodesmacea or sprang from ancient
members of that stock. In this order the elaboration of the hinge-plate
dentition reaches its highest development. Though many of the members
of this order live imbedded in the surface of the sea-bottom, they are more
or less migratory and free-living, and only a few extremely specialized
forms inhabit permanent burrows of their own excavation. They are
sometimes commensal in the burrows of other animals. Similarly, though
often byssiferous, especially when young, few of them fix themselves per-
manently by a byssus.
On the whole it is a rather homogeneous group and does not seem to
warrant division into suborders. Several groups of families appear to be
closely related, and these have been brought together into superfamilies.
KEY TO THE SUPERFAAINLIES OF TELEODESMACEA
(1) Shell sessile, attached to the substratum. Chamacea
(1') Shell not sessile.... 2
(2) Hinge edentulous, pallial sinus distinct. .. .3
(2') Hinge provided with teeth, or if edentulous, then without a pallial sinus. 4
(3) Resilium internal, functional, seated on chondrophores. .Myacea
(3') Resilium vestigial in the left valve or absent. Adesmacea
(4) Hinge scarcely elaborated into a plate, laterals and cardinals more or less conical
and seemingly curving up from below the internal hinge margin.. .Cardiac a
(4') Hinge plate and teeth not as described in 4. .5
(5) Pallial sinus absent. 6
(5') Pallial sinus present, usually well marked, rarely very small. 8
(6) Adductor muscle scars subequal and rounded. 7
(6') Anterior adductor scar narrow and ventrally produced, posterior scar rounded
Lucinacea
(7) Cardinal teeth more or less vertical to the hinge line. .Astartacea
(7') Posterior cardinal extended posteriorly parallel to the hinge line. Carditacea
(8) Resilium internal. Mactracea
(8') Resilium marginal or submarginal. .9
(9) Adductor muscle scars long and thin, dorsally extended. .Solenacea
(9') Adductor muscle scars rounded 10
(10) Pallial sinus largely free from the pallial line ventrally.. Veneracea
(10') Pallial sinus largely concrescent with the pallial line ventrally ........ Tellinacea
SCIENTIFIC SURVEY OF PORTO RICO
Superfamily ASTARTACEA
The hinge plate is well developed. There are two or three cardinals in the
right valve and one to three in the left. The laterals are usually obscure.
When present, they are distant from the cardinals. The ligament may be
external, internal or obsolete. The resilium varies from small and marginal
to large and internal. There is no pallial sinus. The adductor muscle
scars are rounded and subequal. The gills are not united behind the foot,
and the palps are moderate in size. The foot is compressed and grooved
but not byssiferous. The mantle lobes are free ventrally. No definite
siphons are formed, although the anal orifice is usually complete.
Family CRASSATELLIDAE
The outer limb of the gills is smaller and without an appendix. The anal
orifice is sometimes incomplete. The branchial orifice is papillose, func-
tional, but incomplete below. The shell substance is cellulo-crystalline,
with a pronounced epidermis. The valves are somewhat unequal, and
usually more or less rostrate, with the beaks compressed, erect or opistho-
coelous. The ligament is internal and more or less obsolete. The resilium
is large, wholly internal and attached at each end to a chondrophoric pit
in the hinge plate. The lateral laminae and sockets usually alternate in
the valves. The hinge plate is heavy and flat. The posterior cardinal in
the right valve is very small or obsolete, with no distinct socket in the
L 1010
opposite valve. The full cardinal formula is R 10101.
Genus CRASSINELLA Guppy
Crassinella Guppy (1874) Geol. Mag. (2), I: 442.
TYPF (by subsequent designation, Woodring, 1925), Thetis parta C. B. Adams, which may equal Crassatella
marlinicensis d'Orbigny.
The shell is small, flattened, and rounded-triangular. It is slightly
inequilateral, with the posterior dorsal margin excavated. The lunule and
escutcheon are flattened, and the umbones are acute. The sculpture con-
sists of concentric lamellae. The ligament and resilium are internal. The
chondrophore of the resilium is small. There are two cardinals in each
valve. The chondrophore lies between the cardinals in the left valve and
behind them in the right. There is an anterior lateral in the right valve
and a posterior one in the left. In the left valve a low median ridge sepa-
rates the chondrophore from the socket in front of it. The inner margins of
the valves are smooth.
KEY TO THE SPECIES OF CRASSINELLA
(1) Shell very small, somewhat inflated, nearly triangular. C. marlinicensis
(1') Shell small, compressed, slightly rounded anteriorly and attenuate posteriorly
C. guadalupensis
Crassinella martinicensis (d'Orbigny)
PLATE 10, FIGURE 8
Crassatella martinicensis d'Orbigny (1846) Moll. Cubana, 2: 288, PI. 27, figs. 21-23.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
This tiny species is relatively triangular, somewhat inflated, and sculp-
tured with smooth, rounded concentric ridges. It is white or shaded with
light brown.
Length 2.4, height 2.2, width 1.3 mm.
Porto Rico: Mayaguez.
Virgin Islands: Magens Bay, St. Thomas.
Crassinella guadalupensis (d'Orbigny)
PLATE 10, FIGURE 6
Crassatella guadalupensis d'Orbigny (1846) Moll. Cubana, 2: 289, PI. 27. figs. 24-26.
This little shell is slightly larger than the preceding and more irregular
in outline. It is rounded anteriorly and more or less attenuate behind.
It is relatively more compressed. The sculpture is much the same, although
the ridges may be a little sharper. It may be white or variously shaded
with red, brown, or purple.
Length 4, height 3, width 1.5 mm.
Porto Rico: Mayaguez.
Virgin Islands: St. Thomas.
Superfamily CARDITACEA
The hinge plate is well developed and often quite broad. There are,
typically, two cardinals in the left valve and three in the right. The
posterior cardinals are prolonged and extended well back under the liga-
ment, appearing almost like lateral teeth. The laterals are usually obsolete
or absent. The ligament is usually external, rarely internal. The resilium
likewise is usually marginal but rarely internal. There is no pallial sinus.
The adductor muscle scars are rounded and subequal. The gills are united
behind the foot, and the palps are moderate. The foot is compressed and
usually byssiferous. The mantle lobes are free ventrally, and siphons are
not developed.
Family CARDITIDAE
The anatomy is similar to that of the Crassatellidae, but the gills are
united behind the foot and of a very simple reticulate type. The shell
usually has radial sculpture. The pedal muscle scar is adjacent to the
anterior adductor scar. The ligament is external and parivincular. The
resilium usually is included in the ligament, rarely internal. Lateral laminae
and sockets alternate in the valves and are usually obsolete. The anterior
cardinal is often obsolete, the posterior prolonged parallel with the dorsal
L 01010
margin even below the ligament. The full cardinal formula is R 10101'
Genus CARDITA Lamarck
Cardita Lamarck (1799) Mem. Soc. Hist. Nat. Paris, p. 86.
TYPE (by monotypy), Chama calyculata Linnaeus.
The shell is rather mytiliform or elongate-quadrate and is very inequi-
valve. The surface is ornamented with strong radial sculpture. There is a
SCIENTIFIC SURVEY OF PORTO RICO
slight ventral byssal gape. The valve margins are fluted internally except
in the region of the byssal gape. There are three cardinals in the right
valve and two in the left. Laterals may be present or absent.
Cardita gracills Shuttleworth
PLATE 10, FIGURE 7
Cardila gracilis Shuttleworth (1856) Jour. de Conchyl.,
There is a small but distinct anterior lateral in the left valve and a pos-
terior lateral in the right, with corresponding sockets in the opposing hinge
margin. The ribs are nodular and sometimes spinose on the posterior slope.
The shell substance is white internally and shaded with brown or purple.
Length 24, height 10, width 9.5 mm.
Porto Rico: (A.N.S.P., one lot without specific data).
Virgin Islands: St. Thomas.
Superfamily CHAMACEA
These are sessile animals, cemented to the substratum, with the shells
spiral and usually very inequivalve. The hinge plate is heavy and curved.
There are one or two cardinals in the free valve with two and an inter-
mediate socket in the fixed valve. There is frequently a minute or obsolete
posterior lateral. The ligament is external, and the resilium marginal.
There is no pallial sinus. The adductor muscle scars are rounded or elon-
gate and subequal. The gills are plicate, united behind to each other and
to the siphonal septum, so as to form an anal chamber. The palps are
moderate. The foot is small and not byssiferous. The mantle lobes are
united to form separate anal, branchial, and pedal orifices. Siphons are
not produced.
Family CHAMIDAE
The shell substance is three-fold, the inner layer porcellanous and tubular,
the middle obscurely prismatic and the external cellulo-crystaline with
reticulated tubules and an inconspicuous epidermis. The valves are un-
equal, irregular, with one of them sessile. They are closed, usually rounded
in form, and have conspicuous sculpture, often differing in the opposite
valves. The pedal scars are minute, distant. The ligament and resilium
are external in a deep groove, parivincular, and opisthodetic. The area is
distinct and prosodetic. The beaks are more or less spiral and prosogyrous.
The hinge frequently has a minute or obsolete posterior lamina, chiefly in
the fixed valve. The anterior cardinal is broad, usually deeply grooved or
multifid. The posterior one is simple, long, and curved parallel with the
dorsal border. The outer limb of the gills is smaller and appendiculate.
The mantle margin is papillose. The siphonal orifices are not produced
into tubes. The ovary is extensively distributed in the mantle lobes.
The adductors are each composed of two elements.
KEY TO THE GENERA OF CHAMIDAE
(1) Shell nearly equivalve, the valves strongly convex with a large lunule, sculpture
consisting of erect tubular spines on radial ribs................ Echinochama
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
(1') Valves very unequal, the attached one larger, no lunule. .2
(2) Umbones turning from right to left; attached by the left valve .Chama
(2') Umbones turning from left to right; attached by the right valve .Pseudochama
Genus CHAMA Linnaeus
Chama Linnaeus (1758) Syst. Nat., Ed. 10: 691.
TYPE (by subsequent designation, Gray, 1847), Chanu lazarus Li
The shell is orbicular and very inequivalve. It is attached by the left
valve, which is much the larger of the two. The sculpture consists largely
of foliaceous concentric lamellae, which are often supplemented by radial
threads or riblets. The posterior adductor muscle scar is more elongate
than the anterior one.
KEY TO THE SPECIES OF CHAMA
Pallial line passing around anterior end of adductor muscle scar and joining it
anteriorly C. macerophylla
(1') Pallial line joining the scar of the anterior adductor muscle at its ventral posterior
border. .C. sarda
Chama macerophylla Gmelin
PLATE 11, FIGURE 1
Chtama macerophylla Gmelin (1792) Syst. Nat., Ed. 13: 3304.
The surface is ornamented with a variable array of foliaceous lamellations.
There is a varying amount of radial ridges. The inner margin is crenulate
and irregularly shagreened. The coloration shows many combinations of
shading and clouding with white, yellow, red, and purple.
Length 75, height 60, width 45 mm.
Porto Rico: Quebradillas.
Virgin Islands: St. Thomas.
Chama sarda Reeve
PLATE 11, FIGUREs 2, 3
Chama sarda Reeve (1847) Conch. Icon., 4, PI. 7, fig. 40.
The color is white with a variable amount of red. The upper valve is
often extensively clouded with red, and the lower valve is usually red
internally and, to a varying degree, externally as well. The sculpture
consists of irregular concentric foliations and slight radial corrugations.
The internal margin is crenulate. The attached valve is often very deep-
cupped.
Length 27, height 30, width 23 mm.
Porto Rico: San Juan; Mayaguez; San Geronimo; Vieques.
Genus PSEUDOCHAMA Odhner
Pseudochama Odhner (1917) Kungl. Svenska Vetansk. Handl. 52 (16): 28.
TYPE (by subsequent designation, Gardner, 1926), Chama crislella Lamarck.
The members of this genus are very similar to those of the genus Chama,
but appear as mirror images of them. They are attached by the right
SCIENTIFIC SURVEY OF PORTO RICO
valve, and the umbones turn from left to right. This close resemblance
between species attached by the left or the right valve led conchologists to
believe that these animals could attach by either valve. In a study of the
two types, however, Obhner investigated the prodissoconch, the hinge teeth
of very young specimens, and the anatomical features of each type, and
came to the conclusion that two distinct genetic lines were represented. He
proposed the genus Pseudochama for the so-called inverse species.
Pseudochama radians (Lamarck
Chama radiant Lamarck (1819) Anim. s. Vert., 6 (1): 96.
There are two varieties of Pseudochama radians Lamarck in the area under
consideration. The species radians is a smooth heavy shell, clouded and
banded with brown or purple.
KEY TO THE SUBSPECIES OF PSEUDOCHAMA RADIANS
(1) Concentric foliations prominent, coloration usually made up of brown shading
and clouding. P. r. ferruginea
(1') Concentric sculpture reduced and flattened, often with low spinous projections,
coloration typically made up of dark red spotting and striping. P. r. variegata
Pseudochama radians ferruginea (Reeve)
PLATE 11, FIGURE 5
Chama ferruginea Reeve (1846) Conch. Icon., 4, P1. 4, fig. 21.
This species appears almost like a reversed C. macerophylla. The folia-
tions are prominent and are variously shaded with brown and occasionally
with yellow coloration. The inner margin is crenulate.
Length 39, height 39, width 21 mm.
Virgin Islands: St. Thomas.
Pseudochama radians varlegata (Reeve)
PLATE 11, FIGURE 6
Charnma variegata Reeve (1847) Proc. Zool. Soc. London, 14 (166): 118.
The sculpture is much reduced in this form and the red spotting or
striping is characteristic. The present subspecies also closely resembles
one of the members of the typical genus Chama. It appears like a mirror
image of C. congregala.
Length 24, height 30, width 16 mm.
Virgin Islands: St. Thomas.
Genus ECHINOCHAMA Fischer
Echinochama Fischer (1887) Manuel de Conchyliologie, p. 1049.
Typr. (by monotypy), Chama arcinella Linnaeus.
The shell is medium-sized and subequivalve. The adult shells are usually
found free of attachment to the substratum, although they live cemented to
some object during their younger stages. The umbones are strongly proso-
gyrous, and there is a large deep lunule. The external sculpture consists of
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
pits and spinose radial ribs. The prodissoconch is large and elongate. It
is usually fairly distinct in the left valve. The hinge of the right valve is
armed with a heavy, furrowed anterior callosity, a posterior row of denticles
paralleling the ligament, and a rudimentary posterior lateral. The left
valve bears an anterior row of small denticles, a furrowed socket, and a
heavy posterior tooth, which has its upper surface denticulate and its
inner surface furrowed. There is a rudimentary left posterior lateral.
The margins of the valves are coarsely fluted and internally finely cor-
rugated.
Echinochama arcinella (Linnaeus)
PLATE 11, FIGURE 4
Chama arcinella Linnaeus (1767) Syst. Nat., Ed. 12: 1139.
The pitted surface and strong spinose radial ribs will serve to distinguish
this species from all others in the Antillean fauna.
Length 53, height 55, width 40 mm.
Porto Rico: Mayaguez; Ponce.
Virgin Islands: St. Thomas.
Superfamily LUCINACEA
The hinge plate is narrow and arched. The cardinals are variable.
Typically there are two or three cardinals in each valve but they may be
represented by only one in each valve or they may be obsolete or absent.
The laterals consist of one anterior and one posterior tooth in the right
valve, but these may be obsolete or absent. The ligament is external, set
in a groove, with the resilium submarginal. There is no pallial sinus.
The anterior muscle scar is usually narrow and produced ventrally, while
the posterior one is shorter and rounded. The gills are smooth, usually
united behind the foot, forming an anal chamber. Sometimes (in the
Thyasiridae) they are free behind the foot. The palps are small, sometimes
elongated, and sometimes obsolete. The foot is elongate and club-shaped,
not byssiferous except in a few minute forms. The mantle lobes are free
ventrally. The anal siphon is complete and sometimes produced into a
tube. The branchial siphon is often incomplete although occasionally
complete, and, in the Cyrenoididae, it is produced into a tube.
KEY TO THE FAMILIES OF LUCINACEA
(1) Anterior adductor muscle scar separated ventrally from the pallial line. .2
(1') Anterior adductor muscle scar contiguous ventrally with the pallial line. .3
(2) Hinge edentulous or with an obsolete cardinal tooth in the right valve; hepatic
and reproductive glands external to the visceral mass, pedunculated and arbo-
rescent ... .. Thyasiridae
(2) Hinge usually with representatives of both cardinals and laterals although rarely
edentulous; hepatic and reproductive glands included in the visceral mass
Lucinidae
(3) Epidermis conspicuous, anal orifice produced into a tube. Cyrenoididae
(3') Epidermis inconspicuous, anal orifice not tubular. ............... Ungulinidae
SCIENTIFIC SURVEY OF PORTO RICO
Family THYASIRIDAE
The shell substance is earthy, with an inconspicuous epidermis. The
beaks are prosocoelous. The valves are equal, free and closed, with plain
margins. They are smooth or feebly concentrically striated, and usually
with a radial posterior flexure. The adductor muscle scars are similar to
those of the Lucinidac. The pallial area is often punctate. The ligament
and resilium are parivincular, opisthodetic, and subexternal, seated in a
groove. The area is impressed. The hinge is feeble, without lateral lami-
nae, and edentulous or with an obsolete cardinal tooth in the right valve.
The gills have both internal and external direct and reflected laminae. The
external limb of the gills is dorsally directed and they are free behind
the foot. The palps are obsolete. The hepatic and reproductive glands are
external to the visceral mass, pedunculated and arborescent. The foot is
slender and much elongated. The mantle edges are thickened and smooth,
free ventrally. The branchial foramen is incomplete and not produced into
a tube.
Genus THYASIRA Lamarck
Thyasi'a Lamarck (1818) Anim. s. Vert., 5: 492.
TYPE (by monotypy), Tellina flexuwsa Montagu.
The description given for the family will apply, for the most part, to the
genus as well. The hinge is edentulous. The anterior dorsal area is more
or less impressed, and the posterior dorsal area is plicate or radially sulcate.
KEY TO THE SPECIES OF THYASIRA
(1) Posterior slope of shell with two deep, distinct, radial grooves; surface finely
concentrically striated. .... ...... ... T. trisinuata
(1') Posterior slope with one distinct but rather shallow radial groove; surface finely
granular T. conia
Thyasira trlsinuata (d'Orbigny)
PLATE 11, FIGURE 7
Lucina trisinuata d'Orbigny (1846) Moll. Cubana, 2: 300, p]. 27, figs. 46-49.
Cryplodvn obsus Verrill (1872) Am. Jour. Sci., 3: 287, PIl. 7, fig. 2.
The elevated shape, trisinuate posterior slope, and concentrically sculp-
tured surface will distinguish this species from the next one.
Length 12, height 14, width 10 mm.
Porto Rico: Mayaguez.
Thyasira conia Dall and Simpson
PLATE 11, FIGURE 8
Thyajira conia Dall and Simpson (1901) Bull. U. S. Fish Comm., : 490.
The single situation of the posterior slope, together with the finely
granular surface, characterize this species.
Length 6, height 6, width 3 mm.
Porto Rico: San Juan.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Family LUCINIDAE
The shell substance is porcellaneous or chalky, usually with an incon-
spicuous or dehiscent epidermis. The shell is rounded, variably sculptured;
the valves are equal, free, and closed. There are low, prosocoelous beaks.
The adductor and pedal scars may be adjacent or distinct; the latter are
small. The anterior adductor scar is elongated and largely within the
pallial line, which is not sinuate. The inner surface of valves within the
pallial line is often granular or punctate. The cardinal area is small, often
deeply impressed. The ligament and resilium are subinternal, set in a
deep groove, but usually more or less visible externally. The hinge plate is
distinct. The lateral laminae are distant from the cardinals. There are
an anterior and a posterior lateral in the right, and corresponding sockets in
the left valve. The cardinal teeth are radial; formula L010 The
R 0101
posterior cardinal tooth is larger and often bifid, but any or all of the teeth
may be obsolete or absent. The gills have an internal direct and reflected
lamina, without appendix, the external limb absent. The palps are very
small. The hepatic glands are contained within the general visceral mass.
The foot is not grooved and has a terminal mucous gland. The mantle
edges are usually plain and thick. The branchial foramen is papillose,
not tubular, incomplete below. The anal foramen is complete, usually
with a retractile, tubular siphon.
KEY TO THE GENERA OF LUCINIDAE
(1) Surface ornamented by conspicuous divaricating sculpture. Divaricella
(1') Surface sculpture radial or concentric, not divaricating. .2
(2) Hinge edentulous in the adult. .... Lucina
(2') Hinge not edentulous in the adult. .3
(3) Sculpture reticulate, radial elements as well developed as the concentric elements
Codakia
(3') Sculpture principally concentric, sometimes with a few radial grooves or ridges or
obscure radial threads. .. ..4
(4) Hinge of right valve bearing two cardinals. Phacoides
(4') Hinge or right valve with a single cardinal. .Myrtaea
Genus CODAKIA Scopoli
Codakia Scopoli (1777) Introd. Hist. Nat. Lap. Plant Anim., p. 398.
TYPE (by monotypy), Chama codak Adanson Venus punctata Linnaeus.
The shell is large, suborbicular, and moderately or strongly inflated.
The lunule is small and deeply depressed. The sculpture consists of radial
grooves and striae, crossed by incrementals. The ligament and resilium
are large and deeply inset. The hinge of the right valve bears a prominent
anterior lateral, typically, close to the cardinals, an anterior and a middle
cardinal, and a small posterior lateral. The hinge of the left valve consists
of large double anterior laterals, anterior and middle cardinals, and small
double posterior laterals. The inner margins of the valves are slightly
wrinkled.
SCIENTIFIC SURVEY OF PORTO RICO
KEY TO THE SUBGENERA OF CODAKIA
(1) Shell moderately inflated; anterior laterals close to the cardinals. .Codakia s.s.
(1') Shell usually strongly inflated; anterior laterals relatively distant from the car-
dinals.. .Jagonia
Subgenus CODAKIA s.s.
The description is the same as given under the genus, with the limiting
features of the key.
Codakila orbicularis (Linnaeus)
PLATE 12, FIGURE 1
Venus orbicularis Linnaeus (1758) Syst. Nat., ed. 10: 688.
Lucina tigerina Linnaeus: Reeve (1850) Conch. Icon., 6, PI. 1, fig. 3; not Linnaeus (1767).
This large, circular species is easily recognized. It is white and fre-
quently flushed with yellow in the umbonal cavity. The hinge margin is
usually characteristically stained with red.
Length 80, height 70, width 30 mm.
Porto Rico: San Juan; Ponce, Mayaguez; Laiza Vieja; Hucares; San
Geronimo; Puerto Real; N. of Vega Baja; Playa Humacao.
Virgin Islands: Lindbergh Beach, St. Thomas; St. Croix; Tortola; Caneel
Bay, St. John; Virgin Gorda.
Subgenus JAGONIA Recluz
Jagonia Recluz, 1869, Act. Soc. Linn. Bordeaux, 27; 37.
TYPr (by original designation), Le Jagon Adanson = Venus orbiculata Montagu.
The shell is medium-sized, suborbicular, and strongly inflated. The
lunule is small and deeply depressed. The sculpture consists of narrow
radial ribs and narrow concentric beads. The ligament is narrow. The
hinge resembles that of Codakia s.s., but the laterals are more symmetrically
situated with regard to the cardinals and the posterior laterals are stronger.
The inner margin is weakly frilled.
KEY TO THE SPECIES OF SUBGENUS JAGONIA
(1) Radial ribs irregular, not strongly delimited, often threadlike; surface not strongly
beaded .C. costala
(1') Radial ribs pronounced; surface often distinctly beaded. 2
(2) Shell circular in outline. .C. orbiculata
(2') Shell not circular in outline .3
(3) Shell subcircular but with the hinge line flattened. C. pectinella
(3') Shell subcircular but somewhat oblique. C. porloricana
Codakla (Jagonla) costata (d'Orbigny)
PLATE 12, FIGURE 2
Lucina costly d'Orbigny (18-16) Moll. Cubana, 2: 296, pl. 27, figs. 40-42.
The irregular, often threadlike, radial ribs are distinctive for this species.
They are frequently somewhat prominent in groups, and this is probably the
origin of the specific name.
Length 9, height 8, width 5 mm.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Porto Rico: Ponce; Hucares; Arroyo.
Virgin Islands: St. Thomas; St. Croix; Caneel Bay, St. John; Tortola;
Virgin Gorda.
Codakla (Jagonia) orbiculata (Montagu)
PLATE 12, FIGURE 3
Venus orbiculata IMontagu (1808) Test. Brit. Suppl., p. 42.
Lucina pecten Lamarck (1818) Anim. s. Vert., 5: 543.
This is a circular species, with pronounced beaded radial ribs.
Length 13, height 12, width 5.5 mm.
Porto Rico: Ensenada Honda, Culebra.
Virgin Islands: St. Thomas.
Codakla (Jagonia) pectinella C. B. Adams)
PLATE 12, FIGURE 6
Lucina pectinella C. B. Adams (1852) Contrib. Conch., p. 246.
The radial ribs are well marked and are crossed by fine, sharp, concentric
sculpture. The shell is subcircular, but the hinge line is straightened,
giving the characteristic shape to this species.
Length 7.5, height 8, width 4 mm.
Porto Rico: San Juan; Mayaguez.
Codakla (Jagonia) portoricana Dall
PLATE 12, FIGURE 4
Codakia (Jagonia) porloricana Dall (1901) Proc. U. S. Nat. Mus., 23 (1237): 822, pl. 39, fig. 6.
The radial ribs are more pronounced than the concentric sculpture, but
the most distinctive feature is the oblique shape of the shell.
Length 7.5, height 6.7, width 6 mm.
Porto Rico: San Juan; Mayaguez.
Genus LUCINA Lamarck
Lucina Lamarck (1799) Mem. Soc. Hist. Nat. Paris, p. 84.
TYPE (by monotypy), Venus edentula Linnaeus.
The shell is large, thin, and subspherical. The lunule is small and de-
pressed. There is no escutcheon. The insignificant sculpture is made up
of exaggerated incremental growth lines. The ligament and resilium are
external but deeply inset. The hinge is edentulous, and the inner margins
of the valves are smooth. The anterior adductor muscle scar is long and
parallels the pallial line.
KEY TO THE SPECIES orF LUCINA
(1) Shell tinted with yellow internally, umbones not prominent....... L. chrysostonma
(1') Shell white, umbones relatively more prominent .................... L. phenax
Lucina chrysostoma Philippi
PLATE 12, FIGURE 5
Lucina chrysostoma Phillippi (1845) Zeitschr. f. Malakozool., p. 181.
Lucina edentula of authors, not Linnaeus.
SCIENTIFIC SURVEY OF PORTO RICO
This is a moderately large species, thin and globular in outline. It is
characteristically tinted with yellow internally.
Length 46, height 41, width 28 mm.
Porto Rico: San Juan; Mayaguez; Ponce; Humacao Playa; E. of Boca
de Cangrejos.
Virgin Islands: St. Thomas.
Lucina phenax Dall and Simpson
PLATE 12, FIGURE 8
Lucina phenax Dall and Simpson (1901) Bull. U. S. Fish Comm. 20: 492.
This is a small, thin, white shell with a grayish, papery epidermis. The
umbones are somewhat more prominent than in the preceding species. The
present species bears a superficial resemblance to a young Phacoides pensyl-
vanicus, but has no hinge teeth and much thinner valves.
Length 9, height 8, width 5.5 mm.
Porto Rico: San Juan; Mayaguez.
Genus MYRTAEA Turton
Myrtaea Turton (1822) Conch. Insul. Brit., p. 133
TYPE (by monotypy), Venus spinifera Montagu.
The shell is ovate or subrectangular and not inflated. The sculpture is
chiefly concentric. The lunule and escutcheon are long and narrow. The
ligament and resilium are deep-seated but not internal. The anterior
adductor muscle scar is relatively short. In the hinge the right anterior
cardinal is absent, and the left laterals are frequently obsolete.
Myrtaea pristophora Dall and Simpson
PLATE 12, FIGURE 7
Mlyriaea pristophora Dall and Simpson (1901) Bull. U. 5. Fish Comm., 20: 493, Pl. 55, figs. 4, 6.
The pronounced concentric sculpture is raised into lamellate projections
along the dorsal border of the shell. The color is white. The interior of
the disk is punctate. The margins of the valves are finely radially striate
or smooth.
Length 7, height 7.5, width 4 mm.
Porto Rico: San Juan; Mayaguez.
Genus PHACOIDES Blainville
Phacoides llainville (1825) Man. Mala. et Conch., p. 550.
Lucina Lamarck (1801) not Lamarck (1799).
TYPE (by monotypy), Lucina jamaicensis Lamarck = Tellina pectinata Gmelin.
This genus is made up of most of the species commonly included in
Lucina in the broad sense but not Lucina of Lamarck, 1799. Owing to
the very numerous modifications of characters shown by members of
Phacoides, it is divided into a number of subdivisions. Four of them are
represented in the Porto Rican fauna.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
(1) Dorsal areas developed .2
(1') Dorsal areas obsolete. .Callucina
(2) Cardinal teeth largely effaced or obsolete in the adult. Phacoides s.s.
(2') Cardinal teeth not obsolete in the adult. .3
(3) Sculpture concentric. .Linga
(3') Sculpture reticulate or muricate. .Lucinisca
Subgenus .PHACOIDES s.s.
The shell is subcircular and more or less laterally compressed. There are
strong dorsal areas and the sculpture is chiefly concentric. The cardinal
teeth are obsolete in the adult, but the laterals are well developed.
Phacoides (Phacoides) pectinatus (Gmelin)
PLATE 12, FIGURE 11
Tellina pectinata Gmelin (1792) Syst. Nat., Ed. 13: 3226.
Lucina jamaicensis Lamarck (1818) Anim. s. Vert., 5: 539.
This is a common West Indian shell. It bears a marked resemblance to
Lucina chrysosloma both in shape and in the internal yellow coloration.
It is easily distinguished by the more distinct dorsal areas and the strong
lateral teeth.
Length 55, height 50, width 30 mm.
Porto Rico: San Juan; Ponce; Laiza Vieja; Humacao Playa; Quebradillas;
San Antonio Bridge; Boca Cangrejos.
Virgin Islands: St. Thomas; St. Croix.
Subgenus LINGA de Gregorio
Linga de Gregorio (1884) Bull. Soc. Malac. Italiana, 10: 217.
TYPE, Lucina columbella Lamarck.
The dorsal areas are developed, the lunule often deeply impressed. The
right anterior cardinal is often effaced, but the other teeth are usually well
developed.
KEY TO THE SPECIES OF SUBGENUS LINGA
(1) Dorsal areas strongly developed; surface regularly and evenly concentrically
sculptured. .... .P. pensylvanica
(1') Dorsal areas weakly developed; surface finely concentrically ridged, also with
three or four deeper concentric sulci. P. trisulcata blanda
Phacoldes (Linga) pensylvanica (Linnaeus)
PLATE 12, FIGURE 10
Venus pensylvanica Linnaeus (1758) Syst. Nat., Ed. 10: 688.
This distinct, globular species is a common Antillean bivalve. It exhibits
considerable variation in sculpture and shape, but is not easily confused with
any other species in the region. Sometimes it has orange coloration in-
ternally, and this form has received the varietal name aurantia. This
condition is probably only a response to ecological factors in the environ-
ment.
Length 54, height 53, width 40 mm.
SCIENTIFIC SURVEY OF PORTO RICO
Porto Rico: Mayaguez.
Virgin Islands: Smith's Bay, St. Thomas; St. Croix; Caneel Bay, St.
John; Tortola; Virgin Gorda.
Phacoides (Linga) trisulcatus blandus Dall and Simpson
PLATE 12, FIGURE 9
Phacoides (Here) trisulcalus blandus Dall and Simpson, 1901, Bull. U. S. Fish Comm., 20: 493, Pl. 58, fig. 13.
This is a small, obliquely triangular species. The surface is evenly con-
centrically ridged and characteristically sulcate, with three or four deeper
concentric grooves. There are indications of faint radial grooves. The
dorsal areas are not so pronounced as in the preceding species. The color
is white, sometimes tinged with salmon color. This coloration is probably
of a similar nature to that found in pensylvanica.
The typical trisulcatus Conrad, 1846, (Am. Jour. Sci., 404), is a Miocene
fossil. The recent form is so similar that it is treated as a subspecies.
There are slight differences in shape and sculpture, but they do not seem to
be of sufficient importance to distinguish a separate species.
Length 12, height 13, width 8 mm.
Porto Rico: San Juan.
Virgin Islands: St. Thomas.
Subgenus LUCINISCA Dall
Lucinisca Dall (1901) Proc. U. S. Nat. Mus., 23: 805.
TYPE (by original designation), Lucina nossula Conrad.
The shell is subcircular and laterally compressed. The dorsal areas are
well marked. The sculpture is reticulate and muricate. The right anterior
cardinal is obsolete.
Phacoides (Lucinisca) muricatus (Spengler)
PLATE 13, FIGURE 1
Tellina muricala Spengler (1798) Skrift. Nat. Selsk., p. 120.
Lucina scabra Lamarck (1819) Anim. s. Vert., 6: 542.
The beautiful sculpture of this species is distinctive. The spinous proc-
esses on the radial ribs are present over the whole external surface of the
shell. The color is white.
Length 13, height 12, width 4 mm.
Porto Rico: Mayaguez.
Virgin Islands: St. Thomas.
Subgenus CALLUCINA Dall
Callucina Dall, Proc. U. S. Nat. Mus., 23: 806.
TYPE (by original designation), Lucina radians Conrad.
The shell is subcircular and inflated. The surface is sculptured with
threadlike concentric ridges. Sometimes there are feeble traces of radial
sculpture. The dorsal areas are obsolete. There is a very small lunule.
There is one cardinal tooth in each valve. The inner margins of the valves
are crenulate.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Phacoides (Callucina) radians (Conrad)
PLATE 13, FIGURE 3
Lucina radians Conrad (1841) Am. Jour. Sci.,
This little shell has a superficial resemblance to the members of the
venerid genus Dosinia. The anterior laterals are obscure, and the posterior
laterals are virtually absent. The lunule is small and chiefly in one valve,
fitting, when closed, into a recess in the other valve. The shell color is
white, sometimes tinged with yellow.
Length 18, height 17.5, width 10 mm.
Porto Rico: San Geronimo.
Genus DIVARICELLA von Martens
Divaricello von Martens (1880) Beitrage zur Meersfauna der Insel Mauritius und der Seychellen, p. 321.
TYPE (by monotypy), Lucina (Divaricella) angulijera von Martens = Lucina ornate Reeve.
The shell is medium-sized, orbicular, and strongly inflated. The umbones
are low, and the lunule is small although moderately deep. The sculpture
consists of oblique grooves angulated along a line extending obliquely
downward and forward from the umbones. The ligament and resilium are
united and deeply inset. The hinge of the right valve bears a narrow
anterior cardinal, a heavy middle cardinal, and an anterior and a posterior
cardinal, a heavy middle cardinal, and an anterior and a posterior lateral.
In the left valve there is a heavy anterior cardinal, a narrow posterior
cardinal, and double anterior and posterior laterals. The posterior laterals
are much farther from the cardinals than the anterior ones are. The inner
margins of the valves are smooth or finely fluted. The anterior adductor
muscle scar is long and parallels the pallial line.
KEY TO THE SPECIES OF DIVARICELLA
(1) Inner margin smooth... .D. dentata
(1') Inner margins finely fluted or crenulate. .D. quadrisldcata
Divaricella dentata (Wood)
PLATE 13, FIGURE 5
Tellina denlata Wood (1815) General Conchol. p. 195.
This species averages a little larger in size than quadrisulcata. The
inner margin is smooth. The divaricating ridges of the surface sculpture
are usually elevated into dentate projections dorsally near the hinge line.
The specific name is suggested by this character. Both this species and
quadrisulcata have the periodic concentric sulcations from which the latter
derives its specific name. The shell is pure white.
Length 30, height 29, width 17.5 mm.
Virgin Islands: Lindbergh Beach, St. Thomas; St. Croix; Tortola.
Divaricella quadrisulcata (d'Orbigny)
PLATE 13, FIGURE 8
Lucina quadrisulcala d'Orbigny (1846) Voy. I'Amer. Merid., 584.
SCIENTIFIC SURVEY OF PORTO RICO
This is a white, divaricately sculptured species which very closely re-
sembles the preceding one. The inner margins are finely fluted or crenulate,
and the dentations of the dorsal margin are lacking. It is also somewhat
smaller.
Length 25, height 24, width 14 mm.
Porto Rico: Hucares.
Virgin Islands: St. Thomas; St. Croix; Caneel Bay, St. John; Tortola;
Virgin Gorda.
Family UNGULINIDAE
The adductor scars are continuous peripherally with the pallial line.
The hinge has the laterals obscure or absent. The valve margins are plain.
The shell is orbicular in outline, rarely irregular in nestling forms. The
anatomy is like that of the Lucinidae, but with the external limb of the gill
developed, reflected, and sometimes appendiculate. The anal foramen is
not tubular.
Genus TARAS Risso
Taras Risso (1826) Hist. Nat. Eur. Merid., 4: 344.
Diplodoana Bronn (1831) Ital. Tert.-Gebild. u. Einschl., p. 12.
TYPE (by monotypy), Taras antiqualus Risso.
The shell is thin and orbicular, strongly inflated. The surface is finely
concentrically striate or pustulose. There are two cardinals in each valve.
The left anterior one and the right posterior one are bifid. The laterals
are obscure or absent.
KEY TO THE SUBGENERA OF TARAS
(1) Sculpture consisting of concentric incremental lines. .. Taras s.s.
(1') Sculpture consisting of incrementals and minute pustules. .Phlyctiderma
Subgenus TARAS s.s.
The characters are as given for the genus, with the limiting features of
the key.
KEY TO THE SPECIES OF TARAS S.S.
(1) Shell subcircular; very small. T. nudeiformis
(1') Shell subquadrate; relatively large .......... T. punctala
Taras (Taras) punctata (Say)
PLATE 13, FIGURE 4
Amphidesma punctala Say (1822) Jour. Acad. Nat. Sci. Phila., 308.
Lucina janeirensis Reeve (1850) Conch. Icon., PI. 8, fig. 43.
Mysia pellucida Heilprin (1889) The Bermuda Islands, pp. 179, 190. PI. 17, fig. 3.
The rounded subquadrate shape and somewhat attenuate anterior end
are characteristic for this species. The surface is ornamented with a
microscopic sculpture of short radiating striulae, minutely punctate where
well developed. This type of ornamentation is apparently peculiar to the
species. Dall has suggested that it may bridge the gap between the Taras
McLEAN: BII'ALI'E MOLLUSKS OF PORTO RICO
proper and Phlyctiderma. The color is white, although sometimes more or
less yellowed.
Length 17.5, height 16, width 12 mm.
Virgin Islands: St. Thomas.
Taras (Taras) nucleiformis (Wagner)
PLATE 13, FIGURE 7
M.ysia nucleiformis Wagner (1838) Jour. Acad. Nat. Sci. Phila.. 8: 52, PI. 1, fig. 4.
Cytherea sphaerica H. C. Lea (1845) Trans. Am. Phil. Soc. (2), 9: 241. PI. 34, fig. 22.
This is a small, subglobose species with very fine concentric sculpture.
The hinge is very much concentrated, but the dentition is normal. The
shell is moderately heavy, and the altitude is about equal to the length.
Length 6.3, height 6 mm.
Porto Rico: Mayaguez; Culebra.
Virgin Islands: St. Thomas.
Subgenus PHLYCTIDERMA Dall
Phlycliderma Dall (1899) Jour. of Conch., 9: 244.
TYPE (by original designation), Diplodonta semiaspera Philippi.
The shell is small, suborbicular, and strongly inflated. The sculpture
consists of incremental lines and minute pustules. The ligament and
resilium are external. There is a heavy anterior cardinal and a heavy,
oblique, bifid posterior cardinal in the right valve. The left valve has a
heavy, bifid anterior cardinal and a narrow, elongate posterior cardinal.
KEY TO THE SPECIES OF PHLYCTIDERMA
(1) Shell relatively coarsely punctate or pustulose. T semiaspera
(1') Shell minutely pitted. .. ...... .2
(2) Width a little more than one-third the length. T notata
(2') Width about two-thirds the length ...... T gabbi
Taras (Phlyctiderma) semlaspera (Philippi)
PLATE 13, FIGURE 6
Diplodonia semiaspera Philippi (1836) Arch. f. Naturg.,
This is a tumid, robust species with distinct pustulose sculpture. The
hinge is typical for the subgenus. The adductor muscle scars in this species
are very large. The color is white, sometimes faintly tinted with light
straw-color.
Length 14.5, height 13, width 10 mm.
Virgin Islands: Lindbergh Beach, St. Thomas.
Taras (Phlyctiderma) gabbi (Dall)
PLATE 13, FIGURE 9
Mysia subquadrata Gabb (1873) Trans. Am. Phil Soc n.s. 15: not Diplodonia subquadrata Carpenter,
1855.
D. [iplodontal gabbi Dall (1900) Trans. Wagner Free Inst. Sci. Philadelphia, 3 (5): 1183, footnote
Diplodonia (Phlyctiderma) puncturella Dall (1900) op. cit., p. 1183, Pl. 45, fig. 26.
SCIENTIFIC SURVEY OF PORTO RICO
This is a small, thin, moderately convex species. The outline is rounded
or very slightly subquadrate. The length and height are about equal.
The umbones are small but prominent with the hinge line sloping equally
on both sides. The surface is very finely pitted. It is white, although
sometimes generally tinged with light brown shading.
Length 6.5, height 6.7, width 4 mm.
Porto Rico: San Juan.
Virgin Islands: St. Thomas.
Taras (Phlyctiderma) notata (Dall and Simpson)
PLATE 13, FIGURE 10
Diplodonia notala Dall and Simpson (1901) Bull. U. S. Fish Comm., 20:
This species somewhat resembles the preceding one in general shape and
appearance, but is much more compressed laterally. The umbones are
nearly central. They are scarcely inflated. The surface punctations are
very fine. The color is white.
Length 9, height 8.5, width 3.5 mm.
Porto Rico: Mayaguez.
Family CYRENOIDIDAE
The shell is similar to the type found in the Ungulinidae, but has a con-
spicuous epidermis. The pallial area is smooth. There are no lateral
laminae. Typically there are three cardinals in each valve, although two
pairs of these may be united dorsally and the anterior left cardinal is usually
obsolete. The gills have both inner and outer direct and reflected laminae.
The outer limb is smaller and the gills are united behind as in Lucina.
The palps are elongate. The mantle edges are plain. Both siphons are
developed and elongate. They are united to their tips and contractile.
Genus CYRENOIDA de Joannis
Cyrenoida de Joannis (1835) Mag. Zool.. 5, PI. 64.
Cyrenella Deshayes (1835) Mag. Zool., 5, Pl. 70.
TYPE (by monotypy), Cyrenoida duponlia de Joannis.
The shell is thin and orbicular. The umbones are somewhat inflated,
prosogyrous, and located well anterior of the midline. Two cardinals
united dorsally in each valve are in the shape of an inverted numeral seven.
In the right valve there is a small V-shaped or laminar cardinal below.
There are no laterals. The adductor muscle scars resemble those found in
the Lucinidae.
Cyrenoida americana (Morelet)
PLATE 13, FIGURE 2
Cyrenoides americanus Morelct, -51, Test. Nov., 26.
This shell bears a superficial resemblance to that in the members of the
genus Taras. It differs by the conspicuous epidermis and the very char-
acteristic cardinal teeth united dorsally so as to resemble an inverted
1HcLE, BIVALV'E MOLLUSKS OF PORTO RICO
number seven. The anterior cardinal is elongate and produced and ap-
pears almost like a lateral butit has its origin beneath the umbo and so is a
true cardinal. The sculpture is concentric and fairly conspicuous, recalling
some of the fresh-water Corbiculidae.
Length 19, height 18, width 12 mm.
Porto Rico: Arecibo.
Superfamily CARDIACEA
Hinge plate arched, very narrow. The margin is scarcely elaborated
into a definite hinge plate. Fundamentally there are two simple cardinals
in each valve, although one in each valve may be obsolete. The complete
hinge includes one anterior and one posterior lateral in the left valve and
two anterior and one posterior lateral in the right. The resilium is external
and marginal. There is no pallial sinus except in the Adacnidae. The
adductor muscle scars are rounded and subequal. The gills are strongly
plicate and united behind, forming an anal chamber. The palps are large.
The foot is elongate, keeled and geniculate. A byssal gland is present,
but no byssus is developed. The mantle lobes are free ventrally. Siphons
are formed but not produced into tubes except in the Adacnidae.
Family CARDIIDAE
The shell substance is cellulo-crystalline, with the external layer more or
less tubular; with a variable epidermis. The valves are equal, free, and
gaping slightly behind. The beaks are prosocoelous. The margins are
usually serrate or radially striated. The pedal muscle scar is distinct and
usually distant from that of the adductor. The ligament and resilium are
parivincular, short, external, and set in a groove. The area is obscure.
The teeth are simple, smooth, never bifid. One cardinal in each valve is
usually persistent, the others inconstant. The gills have a very simple
type of reticulation; sometimes the outer limb is much produced dorsally.
The siphonal septum is sometimes much produced anteriorly above the
gills. The palps are large and not united distally. The foot is grooved
and capable of being flattened to serve as a fulcrum. The mantle edges are
papillose. The anal foramen has a well-developed valve but no siphons.
The branchial foramen is large, usually complete. The perisiphonal area
is profusely papillose.
KEY TO THE GENERA OF CARDIIDAE
(1) Shell distinctly sculptured. .2
(1') Shell nearly smooth. Laevicardium
(2) Shell with two distinctly separated areas of sculpture. .Microcardium
(2') Shell more or less uniformly sculptured. .3
(3) Shell very thin; distinctly longer than high.. .Papyridea
(3') Shell not particularly thin; subcircular or higher than long. .4
(4) Shell with 21 ribs or less, or, if with more than 21 ribs, then shell abruptly flat-
tened posteriorly Trigoniocardia
(4') Shell with 22 ribs or more; usually gently rounded or but very slightly flattened
posteriorly.............................................. Cardium
SCIENTIFIC SURVEY OF PORTO RICO
Genus CARDIUM Linnaeus
Cardium Linnaeus (1758) Syst. Nat., Ed. 10: 678.
TYPE (by subsequent designation, Children, 1823), Cardium costatum Linnaeus.
The shell is variably sculptured, usually with a predominantly radial
ornamentation. It is usually closed or slightly gaping. There is no lunule
or escutcheon. The pallial line is simple and rather distant from the
margins of the valves.
There are other subgenera represented in the western Atlantic, but all
the species recorded from Porto Rico and the Virgin Islands fall into the
subgenus Trachycardium.
Subgenus TRACHYCARDIUM MSrch
Trachycardium M1rch (1853) Cat. Yoldi, 2: 34.
TYPE (by subsequent designation, von Martens, 1870), Cardium isocardia Linnaeus.
KEY TO THE SPECIES OF SUBGENUS TRACHYCARDIUM
(1) Ribs smooth or with slight creation or tuberculation .... .C. magnum
(1') Ribs with sharp scales. ........ .2
(2) Scales quite short; interior of shell white or slightly colored; shell subcircular in
outline. ..... ....C. muricatum
(2') Scales long; interior of shell stained with red or purple; shell elongate-ovate in
outline. .C. isocardia
Cardlum (Trachycardium) isocardia Linnaeus
PLATE 14, FIGURE 1
Cardium isocardia Linnaeus (1758) Syst. Nat., Ed. 10: 679.
Cardium eburniferum Guppy (1875) Ann. Mag. Nat. Hist., 51, PI. 7 fig. 3.
This is a large, strongly sculptured species with conspicuous scales.
They are short and thick anteriorly, and long, flattened, and vaulted
posteriorly. The margin is denticulate. The color is yellowish white,
tinted here and there with purple-brown. The interior is white, usually
deeply stained with red or purple, especially beneath the disk and up under
the umbones.
Length 40, height 51, width 35 mm.
Porto Rico: Mayaguez; Humacao; Boca Prieta.
Virgin Islands: St. Thomas; St. Croix; Caneel Bay, St. John; Tortola.
Cardium (Trachycardium) muricatum Linnaeus
PLATE 14, FIGURE 3
Cardium muricalum Linnaeus (1758) Syst. Nat., Ed. 10: 680.
This species is distinguished from the preceding by the much less pro-
nounced sculpture and the subcircular shape. The color is whitish or
yellowish, tinted here and there with orange or light brown. The interior
is white, sometimes tinted with yellow. There are usually two very char-
acteristic reddish-yellow streaks which have their origin in the cavity of
the umbones and fade out a short distance down the shell.
Length 40, height 41.5, width 28 mm.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Porto Rico: San Juan; Mayaguez; Ponce; Humacao; San Antonio Bridge;
Guanica; Rio Herrara near Loiza Vieja; San Geronimo; N. of Veja Baja.
Virgin Islands: Charlotte Amalie, St. Thomas; Caneel Bay, St. John;
Tortola.
Cardlum (Trachycardium) magnum Linnaeus
PLATE 14, FIGURE 2
Cardium magnum Linnaeus (1758) Syst. Nat., Ed. 10: 680.
Cardium leucostomum Born (1780) Mus. Caes. Vind., p. 46, P1. 3, fig. 6.
Cardium subelongatum Sowerby (1840) Proc. Zool. Soc. London, 8: 108.
The ribs of this form are relatively smooth except for slight crenulations
on the anterior ones and a few small tubercles on the posterior ones. The
color is whitish or yellowish, variously stained and spotted with red and
brown. The interior is white, frequently tinted with yellow near the
margin and orange beneath the disk. This species occasionally has the
two rays of color beneath the umbones as in muricatum.
Length 44, height 54.5, width 32.5 mm.
Porto Rico: Humacao.
Virgin Islands: St. Thomas; St. Croix; Caneel Bay, St. John; Tortola;
Virgin Gorda.
Genus PAPYRIDEA Swainson
Papyridea Swainson (1840) Treat. Malacol., p. 374.
TYPE (by subsequent designation, Gray, 1847), Cardium solenijorme Bruguiere, Cardium hiatus Meuschen
The valves are elongate-oval, gaping, and moderately ventricose or
flattened. The posterior portion of the shell is much longer than the
anterior portion which is unusual in this family. The ribs are numerous
and often more or less tuberculose or spiny.
KEY TO THE SPECIES OF PAPYRIDEA
(1) Shell rounded, oval; posterior margin not strongly denticulate. ..... .P.hiats
(1') Shell more rectangular than above species; posterior margin strongly denticulate
P. semisidcalum
Papyridea hiatus (Meuschen)
PLATE 15, FIGURE 1
Cardium spinosum Meuschen (1787) Mus. Gevers., p. 442: not Cardium spinosum Solander, 1786.
Cardium hiatus Meuschen (1787) op. cil., p. 442.
Cardium hiulcum Reeve (1845) Conch. Icon., 2, Cardium fig.
Cardium bullatum of authors not Linnaeus.
The shell is inequilateral and very thin. It is gaping at both ends.
The ribs are numerous, the anterior ones crenulated and the posterior ones
with light scales. The shell is white, variously mottled with red, yellow,
and purple.
Length 41, height 31, width 20 mm.
Porto Rico: San Juan. /, .
Virgin Islands: St. Thomas; Tortola. A IS t.
SCIENTIFIC SURVEY OF PORTO RICO
Papyridea semisulcaturn (Gray)
PLATE 15, FIGURE 2
Cardium semisulcatum Gray (1825) Annals of Philosophy, 25: 138.
Cardium ringiculum Sowerby (1841) Proc. Zool. Soc. London, 8: 106.
Cardium petilanum d'Orbigny (1846) Moll. Cubana, 2: 337, Pl. 27, figs. 50-52.
This is a very thin and fragile shell. The interstices between the posterior
ribs are cut back so as to give the pronounced denticulation of this species.
The shell is usually yellowish white, both exterior and interior sometimes
stained with orange or rose, especially on the posterior side.
Length 13, height 9, width 7 mm.
Porto Rico: San Juan; Boca Prieta.
Virgin Islands: St. Thomas; Virgin Gorda.
Genus TRIGONIOCARDIA Dall
Trigoniocardia Dall (1900) Trans. Wa-ner Free Inst. Sci. Philadelphia, 3 (5): 1075.
Type (by original designation), Cardium graniferum Broderip and Sowerby.
The shells are typically small and few-ribbed; the medial ribs are very
strong. The posterior end is subtruncate, with smaller, closer ribs. The
channels between the ribs are strongly concentrically sculptured.
(1) Hinge with the anterior laterals relatively close to the cardinals and the posterior
laterals more remote Trigoniocardia s.s.
(1') Hinge with the anterior laterals almost as far removed from the cardinals as the
posterior laterals. A mericardia
Subgenus TRIGONIOCARDIA s.s.
The characters for the subgenus are those given under the genus, with
the limiting features of the key.
KEY TO THE SPECIES OF TRIGONIOCARDIA S.S.
(1) Shell rounded, usually with 21 radial ribs, the four middle ribs not greatly larger
than the others. T antillorumn
(1') Shell more triangular than in the preceding form, usually with 18 radial ribs, the
four middle ribs much larger in proportion to the others. T. ceramidum
Trigonlocardia (Trigoniocardia) antillarum (d'Orbigny)
PLATE 14, FIGURE 4
Cardium antillarum d'Orbigny (1846) Mloll. Cubana, 2: 338, PI. 27, figs. 53-55.
Carditum guippyi Thicle (1910) /.ool. Jahrb., Suppl. 11: 129, PI. 9, fig. 25-26.
The shell is rounded and almost subcircular, although it is obliquely
truncated posteriorly. There are about 21 ribs, which are not markedly
different in size. The color is white.
Length 11, height 10, width 8 mm.
Porto Rico: San Juan; Mayaguez.
Virgin Islands: Cancel Bay, St. John; Tortola; Virgin Gorda.
Trigoniocardia (Trigoniocardia) ceramldum (Dall)
I'LATE 14, FIGURE 7
Cardium coramidum Dall (1SS6) Bull. Mus. Comp. Zool.. 12: 269, PI. 4, fig. 6.
McLEAN: BIV ILVE MOLLUSKS OF PORTO RICO
The shell is subtriangular in this species, and there are usually 18 ribs.
The four middle ones are much larger than the rest. The sculpture in the
interspaces between the ribs is quite noticeable. The color of the shell is
white.
Length 8.2, height 8.2, width 8 mm.
Porto Rico: Mayaguez.
Virgin Islands: St. Thomas.
Subgenus AMERICARDIA Stewart
Americardia Stewart (1930) Acad. Nat. Sci. Phila., Special Publ. 3: 267.
TYPE (by original designation), Cardi m medium Linnaeus.
The shell and hinge plate are fairly heavy. The cardinal teeth are un-
equal. The anterior laterals are almost as far removed from the cardinals
as are the posterior laterals.
Trigoniocardia (Americardia) medium (Linnaeus)
PLATE 14, FIGURE 6
Cardium medium Linnaeus (1758) Syst. Nat., Ed. 10: 678.
The shell is somewhat squarely cordate, rounded anteriorly, and con-
cavely angulated posteriorly. There are about 36 narrow radial ribs.
The anterior ribs are covered with short scales. The color is white, variously
clouded and spotted with reddish brown. The interior is white. This
species is quite variable in the amount of depression of the posterior area
and in the elevation of the upper part of the posterior margin projecting
from the central part of the depression when the valves are closed.
Length 34, height 40, width 33 mm.
Porto Rico: Mayaguez; Ponce; Vieques.
Virgin Islands: Charlotte Amalie, St. Thomas; St. Croix; Caneel Bay,
St. John; Tortola; Virgin Gorda.
Genus LAEVICARDIUM Swainson
Laericardium Swainson (1840) Treat. Malacol., p. 373.
Liocardium Mbrch (1853) Cat. Yoldi, 2: 35.
TYPE (by subsequent designation, Stoliczka, 1871), Cardium oblongum Gmelin.
The shell is of relatively great altitude, rounded or oval, and not gaping.
The middle of the valves is smooth or feebly radially striate, and the ends
of the valves have noticeable smooth areas. The anterior laterals arise
from the umbonal cavity.
The members of this genus found in the Porto Rican region seem to fall
into one variable species.
KEY TO THE SPECIES AND SUBSPECIES OF LAEVICARDIUM
(1) Shell rounded, subcircular, with narrow brown radial lines. .L. 1. multilineatum
(1') Shell oblique, oblong; color pattern irregular .2
(2) Shell small, less than 22 mm. in height; umbones pink with some pink flecks and
shading on the disk. .L. 1. sybarilicum
(2') Shell larger, adult greater than 22 mm. in height; variously shaded and marked
with pink, yellow, and brown ....................... . . L. laevigatum
SCIENTIFIC SURVEY OF PORTO RICO
Laevicardium laevigatum (Linnaeus)
PLATE 14, FIGURE 8
Cardium lacrigalum Linnaeus (1738) Syst. Nat., Ed. 10: 680.
Cardium serratum of authors not Linnaeus.
Cardium citrinum Wood (1815) General Conch., p. 223, Pl. 54, fig. 3.
The shell is thin, ovate, and oblique. The surface is smooth; occasionally
there are obsolete radial striae. The inner margin is serrate. The exterior
is colored with a great variety of pink, yellow, and brown shading and
marking. The interior is white, often clouded with pink, yellow, or brown.
The epidermis is light straw-colored, often inconspicuous.
Length 38, height 45.5, width 30 mm.
Porto Rico: Mayaguez; Ponce; Loiza Vieja; Vieques; Culebra.
Virgin Islands: Lindbergh Beach, St. Thomas; St. Croix; Caneel Bay,
St. John; Tortola; Virgin Gorda.
Laevicardium laevigatum sybariticum (Dall)
PLATE 14, FIGURE 5
Cardium serratum sybariticum Dall (1886) Bull. Mus. Comp. Zobl., 12 (6): 70.
This is a small, thin, deep-water subspecies. The shell is ovate, some-
times slightly subquadrate. It is of a translucent white color, with a deep
pink flush on the umbones, and pink flecks on the disk of some specimens.
Length 11.5, height 13.5, width 8 mm.
Porto Rico: Mayaguez.
Laevicardium laevlgatum multillneatum (Dall and Simpson)
PLATE 15, FIGURE 3
Cardium serratum mullilinealum Dall and Simpson (1901) Bull. U.S. Fish Comm., 20: 489.
This large, circular shell, with fine, distinct radial lines, is easy to recog-
nize. It is quite common in the Porto Rican and Virgin Islands area.
There are specimens of typical laevigatum which approximate it in shape
but they do not have the brown radial lines. This subspecies has been
synonymized with the typical subspecies but since it occurs in a definite
geographical area and seems to represent a distinct population, it is thought
better to retain it as a separate entity.
Length 40, height 45, width 32 mm.
Porto Rico: Mayaguez; Ponce.
Virgin Islands: St. Thomas.
Genus MICROCARDIUM Thiele
.llicrocar'dum Thiele (1935) llandb. S.vst. Weichticrkunde, Pt. 3: 878.
TvYP (by subsequent designation, Keen, 1937), Cardium (Pulvia) prrmabile Dall.
The shell is thin and usually small and rounded, sometimes slightly
truncated posteriorly. It is equivalve, almost equilateral, and does not
gape posteriorly. The surface sculpture is predominantly radial, with an
area of reticulate or spinose ornamentation on the posterior slope.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
KEY TO THE SPECIES OF MICROCARDIUM
(1) Shell generally white; about 90 minute ribs .......... A. peramabile
(1') Shell with color; more than 150 minute ribs............ ... ... lincturm
Microcardium peramabile (Dall)
PLATE 15, FIGURE 5
Cardium peramabile Dall (1881) Bull Mus. Comp. Zohl., 9: 132.
The shell is quite tumid. The surface sculpture is divided into two
distinct zones. The anterior three-fifths of the shell is provided with fine
radiating ribs which are crossed with even finer concentric lines, leaving the
surface minutely beaded. At the posterior margin of this area there is a
larger rib which marks off this zone of sculpture. Behind this the ribs
are finer and more widely spaced. There are occasional scales in this area
which have their origin in the interspaces between the ribs.
Length 10, height 11, width 9 mm.
Porto Rico: Mayaguez; Aguadilla.
Virgin Islands: St. Croix.
Microcardium tinctum (Dall)
PLATE 15, FIGURE 6
Cardium peramabile var. linctum Dall (1886) Bull. Mus. Comp. Zol61. 12: 270.
This species is much like the preceding, but the areas of sculpture are
not quite so distinctly marked off, and the ribs are much finer and more
numerous. There are more spines or scales on the ribs in the posterior
area of sculpture. The color is white, beautifully tinted and clouded with
pink or red.
Length 13, height 12, width 9 mm.
Porto Rico: Mayaguez.
Virgin Islands: St. Croix.
Superfamily VENERACEA
The hinge plate is well developed, often broad and strong. Typically
there are three cardinals in each valve, of which one or more may be bifid.
Occasionally one or more cardinals are obsolete. In specialized forms there
are supplemental cardinals or interlocking rugosities on the hinge plate.
Usually there is a single obsolete lateral in one valve or the hinge is without
laterals. The ligament is external, and the resilium marginal. The pallial
sinus is usually well developed, although occasionally very small. It is
largely free from the pallial line ventrally. The adductor muscle scars are
rounded and subequal. In rare cases the posterior scar is somewhat
larger than the anterior one. The gills are slightly plicated and are united
behind to form an anal chamber. The palps are moderate in size. The
foot is short, compressed, and keeled. There is no byssus. The mantle
lobes are free ventrally except in the Glaucomyidae. The siphons are
distinct. They may be separate or united and are usually long.
SCIENTIFIC SURVEY OF PORTO RICO
KEY TO THE FAMILIES OF VENERACEA
(1) Free-living, equivalve forms with the valves regular and closed; a few rare forms
are burrowing but these have three cardinal teeth in each valve; external sculp-
ture not modified for burrowing Veneridae
(1') Typically burrowing forms, the shell often inequivalve and irregular, frequently
somewhat gaping; three cardinals in the left valve and two in the right; ex-
ternal sculpture often spinose and modified for burrowing. .Petricolidae
Family VENERIDAE
The valves are equal, free, and closed, with prosogyrous beaks. They
are variably sculptured, with the margins more or less dentate, except in
the smooth species. The adductor muscle scars are peripheral, with the
pedal scar distant. The pallial sinus is more or less sinuated. The area
is very distinct. The resilium is usually external, embraced by the liga-
ment. The cardinals are frequently bifid, usually radially disposed and
subequal in size except the posterior left one, which is often obsolete or
obscure. The outer gill is smaller and frequently has a dorsal appendix.
The palps are free behind. In the typical forms the foot is not grooved or
byssiferous. The mantle edge is duplex and papillose. The siphons have
papillose orifices; the anal one has a distal valve, and the branchial one is
larger and has a small curtain valve proximally located.
There have been various schemes proposed for incorporating the genera
of this family into subfamilies. However, there is little agreement between
the various suggestions along this line, and for the purposes of the present
work it seems best to treat them merely as a series of related genera.
KEY TO THE GENERA OF VENERIDAE
(1) Anterior lateral teeth present, occasionally small. ... 2
(1') Anterior lateral teeth absent .8
(2) Shell virtually circular .Dosin a
(2') Shell not circular .. ...3
(3) Pallial sinus very small, almost vestigial. .Gafrarium
(3') Pallial sinus moderate or large. .4
(4) Lunule and escutcheon clearly delimited .Antigona
(4') Lunule more or less well defined, but escutcheon not defined, or rarely extremely
faintly so. .5
(5) Inner margin sharply tangentially grooved. Transenella
(5') Inner margin not tangentially grooved.... .6
(6) l'allial sinus acutely angular. ... Pitar
(6') Pallial sinus rounded .7
(7) Shell shape triangular ... Tivela
(7') Shell shape rounded-oval .lMacrocallista
(8) Shell shape circular ... Cyclinella
(8') Shell shape not circular ..9
(9) Valves rostrate posteriorly .. Anomalocardia
(9') Valves rounded or somewhat angular posteriorly but not rostrate.......Chione
Genus DOSINIA Scopoli
Dosna Sconjli (1777) Intr. list. Nat., p. 399.
TYPE (by monotypy), Chama dosin Adanson; = Dosinia africana HIanley.
The shell is circular and usually much compressed laterally. The surface
is sculptured with concentric grooves. The lunule is well defined but the
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
escutcheon is variable, sometimes distinct and often obsolete. The hinge
plate is very broad. There is an anterior lateral tooth in the left valve,
though in many species it is much reduced. Typically there are three
cardinals in each valve, although one or more may be obsolete. The pallial
sinus is angular and ascending.
Dosinia concentrica (Born)
PLATE 15, FIGURE 4
Venus concentrica Born (1780) Test. Mus. Caes. Vind., p. 71, Pl. 5, fig. 5.
Dosiniafloridana Conrad (1866) Am. Jour. Conch., 2: 280, PI. 15, fig. 4.
Dosinia elegans Conrad: Dall and Simpson (1901) Bull. U. S. Fish Comm., 20: 486.
This fine species is similar to the more northern D. elegans, but is a more
inflated shell, its width being greater in proportion to its other measure-
ments. It is beautifully concentrically sculptured, with about nine ridges
to the centimeter on the central portion of the disk. The color is yellowish
white.
Length 68, height 66, width 31 mm.
Porto Rico: Ponce.
Virgin Islands: Long Bay, St. Thomas.
Genus TRANSENNELLA Dall
Transennella Dall (1883) Proc. U. S. Nat. Mus., 6: 340.
TnE (by monotypy), Cytherea (Transennella ?) conradina Dall.
The shell is small and elongate-oval, somewhat pointed posteriorly.
There are three cardinals in each valve. The middle left cardinal is bifid.
There is an elongate left anterior lateral. The lunule is defined, but not the
escutcheon. The pallial sinus is obliquely ascending and angular. The
inner margins of the valves are sharply tangentially grooved.
KEY TO THE SPECIES OF TRANSENNELLA
(1) Surface irregularly concentrically ridged; color white, generally with a few brown
markings. T. cubaniana
(1') Surface obsoletely, minutely, concentrically undulated; color light yellow-brown
T. cidebrana
Transennella cubaniana (d'Orbigny)
PLATE 15, FIGURE 8
Venus cubaniana d'Orbigny (1846) Moll. Cubana, 2, PI. 26, figs. 44-46.
This species is more ovate in shape than the next one, and the concentric
sculpture of the surface is more pronounced. The brown flecking is also
of diagnostic value.
Length 8, height 6, width 4 mm.
Porto Rico: Mayaguez.
Transennella culebrana (Dall and Simpson)
PLATE 15, FIGURE 7
ieretrix (Transennella) culebrana Dall and Simpson (1901) Bull. U. S. Fish Comm., 20: 486, P1. 55, fig. 5.
SCIENTIFIC SURVEY OF PORTO RICO
This species is subtrigonal, with an obscure surface sculpture. The shell
is white internally, but the exterior is a light yellow-brown.
Length 7, height 5.7, width 3.8 mm.
Porto Rico: Culebra.
Genus TIVELA Link
Tivela Link (1807) Beschr. Nat.-Samml. Univ. Rostock, Pt. 2, p. 152.
TYPE (by subsequent designation, Dall, 1902), Venus corbicula Gmelin: Venus mactroides Born.
The shell is solid, trigonal, and subequilateral. The surface is smooth.
The beaks are prominent, and the ligament is short. The lunule is large
but faintly defined. The escutcheon is not defined. The pallial sinus is
small, free, and rounded in front. The hinge bears anterior laterals and
from three to six cardinals. Some cardinals may be rugose, and some
bifid.
Tivela mactroldes (Born)
PLATE 15, FIGURE 9
Venus maarsides Born (1778) Indes Mus. Caes. Vind., p. 53.
Venus corbicula Gmelin (1792) Syst. Nat., Ed. 13: 3278.
This triangular species is not easily mistaken for any other in the region.
It is variously rayed and clouded with brown coloration. In some specimens
the epidermis is pronounced, but in others it is inconspicuous.
Length 47, height 42.5, width 31 mm.
Porto Rico: Humacao Playa; Guayama; Rio Herrara near Loiza Vieja;
E. of Boca de Cangrejos.
Genus GAFRARIUM Reading
Gafrarium Roding (1798) Mus. Bolten.. 2: 176.
TYPE (by subsequent designation, Dall 1902), Venus pectinata Linnaeus.
There are no species of Gafrarium s.s. in the western Atlantic.
This genus is represented by the subgenus Gouldia, which is characterized
as follows.
Subgenus GOULDIA C. B. Adams
Gouldia C. tI. Adams (1847) Cat. Rec. Shells, p. 29.
TYPE (by subsequent designation, Dall, 1902), Thelis cerina C. B. Adams.
The shell is small and trigonal-ovate. The lunule is long, narrow, and
slightly depressed. The sculpture is made up of concentric rugae and less
distinct radial threads. There are two anterior laterals in the right valve
and one in the left. Each valve has three slender cardinals. The pallial
sinus scarcely indents the pallial line. The inner ventral margin is not
fluted, but the inner dorsal margin is grooved.
KEY TO THE SPECIES OF SUBGENUS GOULDIA
(1) Shell about 5 mm. in length; rounded-oval in shape. G. insularis
(1') Shell about 10 mm. in length; rounded-triangular in shape ............ G. cerina
3McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Gafrarium (Gouldia) cerina (C. B. Adams)
PLATE 15, FIGURE 11
Thetis cerina C. B. Adams (1845) Proc. Boston Soc. Nat. Listt, p. 9.
Both this species and the following one are small and have both radial
and concentric sculpture, which gives the surface a cancellate appearance.
Adults of cerina are almost twice the length of adult insularis. This species
is rounded-ovate in shape. The color is white or yellowish white. There
usually are brown markings on the dorsal area and often on the disk as
well.
Length 11, height 9.5, width 4.6 mm.
Porto Rico: Culebra.
Virgin Islands: St. Thomas.
Gafrarium (Gouldia) Insularis (Dall and Simpson)
PLATE 15, FIGURE 10
Circe (Gouldia) insularis Dall and Simpson (1901) Bull. U. S. Fish Comm., 20: 487, PI. 55, fig. 2.
This species is smaller than cerina and much more rounded in outline.
The color is white. Many specimens have a fine sulcus parallel with the
inner margin of the valves.
Length 5.5, height 5, width 3 mm.
Porto Rico: San Juan; Mayaguez.
Genus MACROCALLISTA Meek
Macrocallisla Meek (1876) Rept. U. S. Geol. Surv. Terr., 9: 179.
TYPE (by monotypy), Venus giganeia Gmelin: Venus nimbosa Solander.
The shell is solid, transversely ovate in outline, and polished. The
lunule is well defined, but the escutcheon is indistinct. The pallial sinus
is large and rounded, with a small point in front. It is almost parallel to
the hinge margin. A prominent left anterior lateral tooth is received in a
deep socket in the right valve. There are three cardinals in each valve.
They are smooth and entire except for the right posterior one, which is
bifid.
Macrocallista maculata (Linnaeus)
PLATE 16, FIGURE 1
Venus maculata Linnaeus (1758) Syst. Nat., Ed. 10: 686.
This smooth, rounded-ovate species is very characteristically colored.
The shell substance is white. It is mottled in a vague checkered pattern
with reddish brown. There are two more or less interrupted rays of this
color running obliquely across the disk of the shell from the umbones to the
margin. The epidermis is light straw-colored, giving a yellowish cast to
the exterior.
Length 67, height 50, width 30.5 mm.
Porto Rico: Quebradillas.
Virgin Islands: St. Thomas; Caneel Bay, St. John; Tortola.
SCIENTIFIC SURVEY OF PORTO RICO
Genus PITAR Rbmer
Pilar R6mer (1857) Krit. Untersuch. Moll. Venus, p. 15.
TyPE (by monotypy), Venus lumens Gmelin.
The shell is ovate or trigonal-ovate; concentrically striate or rippled.
The lunule is circumscribed, but the escutcheon is not defined. The inner
margins of the valves are smooth. The pallial sinus is elongate, angular,
and somewhat ascending. There is an anterior lateral in the left valve
which is received into a deep socket in the right valve. Each valve bears
three cardinals. The middle cardinal is stout, the right posterior one is
fairly large and grooved, and the others are slender.
KEY TO THE SUBGENERA OF PITAR
(1) Shell smooth or with concentric striation. ..Pitar s.s.
(1') Shell concentrically laminated. lysteroconcha
Subgenus PITAR s.s.
The characters are the same as given for the genus, with the limiting
features of the key.
KEY TO THE SPECIES OF SUBGENUS PITAR
(1) Shell somewhat rostrate posteriorly .P. aresta
(1') Shell not rostrate posteriorly .. .2
(2) Surface with growth lines but not definite sulci; pallial sinus bluntly angular
P. albida
(2') Surface with concentric sulci; pallial sinus acute.. P. fadminata
Pitar (Pitar) aresta (Dall and Simpson)
PLATE 16, FIGURE 2
.eretrix aresla Dall and Simpson (1901) Bull. U. S. Fish Comm., 20: 485, PI. 56, figs. 1, 7.
The shell is large, solid, and inflated. It is very inequilateral, with
prominent, much incurved, prosogyrous umbones. It is rounded in front
and somewhat rostrate behind. The surface is concentrically sulcate.
The color is white or yellowish white.
Length 51, height 50, width 28 mm.
Porto Rico: Mayaguez; Ponce; Puerto Real.
Pitar (Pitar) albida (Cmelin)
PLATE 16, FIGURE 3
Venus albida Gmelin (1792) Syst. Nat., Ed. 13:
This species is characterized by the presence of concentric growth lines,
not definite sulci. It has a blunt pallial sinus. The shell is more quadrate
posteriorly than that of fulminala. It is typically white, but some speci-
mens have rays of brown coloration.
Length 47, height 38, width 27.5 mm.
Porto Rico: San Juan; Mayaguez.
Virgin Islands: St. Thomas.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Pitar (Pitar) fulminata (Menke)
PLATE 16, FIGURE 4
Cytherea fulminata Menke (1830) Syn. Moll. Mus. Menk., Ed. 2, p. 150.
Cytherea hebraea of authors, not Lamarck.
This species is similar to the preceding one, but has a distinct surface
sculpture of concentric sulci. This sculpture does not always cover the
entire shell, but is present on some parts of the surface. The pallial sinus
is acute, and the shell, as a whole, is more trigonal than that of albida.
The color is white, with radial or zigzag painting of brown coloration.
Length 46, height 38, width 26 mm.
Porto Rico: San Juan.
Virgin Islands: St. Thomas.
Subgenus HYSTEROCONCHA Fischer
Hysteroconcha Fishcher (1887) Man. de Conchyl., p. 1079.
TYPE (by monotypy), Venus dione Linnaeus.
The surface is sculptured with concentric laminae, which frequently
became spinose on the posterior slope of the shell. The pallial sinus is
much wider than in Pitar s.s., and the pallial line is closer to the margin
of the shell. The shell has tinted coloration, not distinct color patterns.
KEY TO THE SPECIES OF SUBGENUS HYSTEROCONCHA
(1) Concentric laminae elevated into spines on the posterior slope of the shell.. P. done
(1') Concentric laminae not elevated into spines ...... .P. circinata
Pitar (Hysteroconcha) done (Linnaeus)
PLATE 16, FIGURE 6
Venus dione Linnaeus (1758) Syst. Nat., Ed. 10: 684.
Dione veneris Reeve (1863) Conch. Icon., 15, P1. 6, fig. 24.
The lamellae are thin and sharp over most of the surface of the shell.
On account of their thin construction they are frequently broken or chipped,
giving them an irregular appearance. On the anterior slope they are ele-
vated into high fragile laminae, and on the posterior slope they are pro-
duced into spines. The basic color is white, largely shaded with pink or
purple coloration.
Length 39, height 32, width 22 mm.
Porto Rico: Humacao Playa; Fajardo; Loiza Vieja.
Pitar (Hysteroconcha) circinata (Born)
PLATE 16, FIGURE 8
Venus circinata Born (1780) Test. Mus. Vind., p. 61, PL 4, fig. 8.
This species is quite similar to the preceding, but the laminae are not
elevated or produced into spines. It is more lightly shaded with pink and
sometimes with an orange coloration.
Length 40, height 33, width 24 mm.
SCIENTIFIC SURVEY OF PORTO RICO
Porto Rico: Mayaguez.
Virgin Islands: St. John.
Genus ANTIGONA Schumacher
Antigona Schumacher (1817) Essai Nouv. Syst. Vers Test., p. 154.
TYPE (by monotypy), Antigona lanellaris Schumacher.
The shell is medium-sized, elongate ovate, with strong, predominantly
concentric sculpture. The lunule is wide, limited by a deep groove. The
escutcheon is long and excavated. It is unequally divided between the
two valves, being larger in the left valve. The umbones are plump. The
ligament is deep-seated. The cardinals are large and partly bifid. There
is a smaller anterior lateral. The inner margins are crenate. The pallial
sinus is small and blunt.
The subgenera represented in the Porto Rican fauna differ in external
sculpture and hinge dentition.
KEY TO THE SUBGENERA OF ANTIGONA
(1) External sculpture made up of concentric lamellae crossed by distinct radial
riblets; right anterior cardinal nearly parallel to the hinge line; right middle
cardinal laminar, deeply bifid. .A ntigona s.s.
(1') External sculpture with little or no radial component; right anterior cardinal
nearly perpendicular to the hinge line; right middle cardinal conical, scarcely
bifid. Ventricola
Subgenus ANTIGONA s.s.
The cancellate sculpture is one character of this subgenus. There are
several minor differences in the hinge teeth between this and the following
subgenus. In Antigona s.s. the laterals are very small and indistinct.
The cardinals are in the form of triangular laminae. In the left valve the
anterior cardinal is grooved on the dorsal edge but not deeply bifid. The
middle cardinal is distinctly bifid. The posterior one is thin and entire.
The right valve has the anterior cardinal entire and the middle and posterior
ones bifid.
Antigona (Antigona) listeri (Gray)
PLATE 16, FIGURE 5
Dosina listeria Gray (1838) The Analyst, 8 (24): 308.
This large, cancellate species is very distinct. The concentric elements
of the sculpture are raised into thin lamellae. The lunule is elongate heart-
shaped. There is sometimes a small amount of purplish brown coloration
under the nymphs or around the posterior muscle scar.
Length 82, height 64, width 49 mm.
Porto Rico: Mayaguez; Ponce.
Virgin Islands; St. Thomas; Tortola; Virgin Gorda.
Subgenus VENTRICOLA Rbmer
Vlntricola R6mer (1867) Mala. Blit., 14: 115.
TYPE (by subsequent designation, Dall, 1902), Venus rugosa Gmeli : Venus rigida Dillwyn.
.McLEAN BIVALVE MOLLUSKS OF P'ORTO RICO
The surface sculpture in this subgenus is predominantly concentric.
The radial element is confined to crenulations of the concentric ribs. The
laterals are small but somewhat larger than in Antigona s.s. The cardinals
are more conical than in that subgenus. In the left valve the anterior
cardinal is heavy, conical, and somewhat sinuated. The middle cardinal is
heavy and bifid, and the posterior cardinal is long, narrow, and practically
parallel with the hinge margin. The right valve has the anterior cardinal
lamellar, rather thin and curved, and almost perpendicular to the hinge
margin. The middle one is large, conical, and vaguely bifid. The posterior
cardinal is long, strong, and bifid.
KEY TO THE SPECIES OF SUBGENUS VENTRICOLA
(1) Large concentric ridges close-set, with one or two fine concentric threads between
them. A. rigida
(1') Large concentric ridges widely spaced, with four or five fine concentric threads
between them.. A. rugalina
Antigona (Ventricola) rigida (Dillwyn)
PLATE 17, FIGURE I
Venus rugosa Gmelin (1792) Syst. Nat., Ed. 13: 3276; not Linnaeus (1758).
Venus rigida Dillwyn (1817) Cat. Shells, 1: 164.
This species is rounded and very tumid. The concentric ribs are very
prominent and close together. There are one or two concentric threads in
each major rib interval. The lunule is deeply sunk and kidney-shaped.
Length 76, height 67, width 59 mm.
Porto Rico: San Juan; Mayaguez.
Virgin Islands: St. Thomas; Tortola.
Antigona (Ventricola) rugatina (Heilprin)
PLATE 16, FIGURE 7
Venus rugatina Heilprin (1887) Trans. Wagner Free Inst Sci. Phila., 1: 92, Pl. 2, fig. 24.
This species also is rounded and very tumid. The concentric ribs are
widely spaced, and there are four or five concentric threads between them.
The lunule is broadly heart-shaped.
Length 27, height 25, width 18 mm.
Porto Rico: Mayaguez.
Genus CYCLINELLA Dall
Cyclinella Dall (1902) Nautilus, 16: 44.
TYPE (by subsequent designation. Dalli 1902) Dosinia tennis Recluz.
The shell is medium-sized, thin, and suborbicular. There is no lunule
and no escutcheon. The surface sculpture consists of growth lines. No
lateral teeth are present. There are three slender cardinals in each valve.
The posterior one is deeply bifid. The pallial sinus is moderately wide and
deep, steeply ascending, the apex narrowly u-shaped.
SCIENTIFIC SURVEY OF PORTO RICO
Cyclinella tenuis (Recluz)
PLATE 17, FIGURE 3
Dosi ic (Artemis) tennis Recluz (1853) Jour. de Conchyl., 3: 250, Pl. 10, fig. 1.
This fine, circular species is easily recognized. The anterior muscle
scar is located more ventrally than in many species, being some distance
from the anterior termination of the hinge line. The shell is a beautiful
translucent white.
Length 42, height 41, width 21 mm.
Porto Rico: Ponce; Mayaguez.
Virgin Islands: St. Thomas.
Genus CHIONE Megerle
Chione Megerle (1811) Ges. naturf. Freunde Berlin, Mag., 5: 51.
TYPE (by subsequent designation, Gray, 1847), Venus dysera Chemnitz = Venus cancellala Linnaeus.
There are no lateral teeth. Each valve has three cardinal teeth. Con-
centric sculpture is dominant, although many species have radial elements
as well. The lunule and escutcheon are defined. The pallial sinus is short
and angular. The inner margins of the valves are crenate.
KEY TO THE SUBGENERA OF CHIONE
(1) Sculpture cancellate. .. ..Chione s.s.
(1') Sculpture made up of broad concentric waves. ... Lirophora
Subgenus CHIONE s.s.
The characters are those given for the genus, with the limiting features
of the key.
KEY TO THE SPECIES OF CHIONE S.S.
(1) Shell small, adult specimens seldom exceeding 15 mm; elongate-oval in shape
C. pygmaea
(1') Shell not small; not elongate-oval .2
(2) Concentric ribs widely spaced, elevated, and frilled over most of the shell; sculp-
ture cancellate. C. cancetlata
(2') Concentric ribs not prominent; sculpture beaded over most of the shell
C. granulata
Chione (Chlone) cancellata (Linnaeus)
PLATE 17, FIGURE 4
Venus cancellata Linnaeus (1767) Syst. Nat., Ed. 12: 1130.
This is one of the most typical bivalve mollusks of the West Indian
fauna. The cancellate surface is very noticeable. The interior is variously
shaded with pink, red, or purple.
Length 38, height 30, width 25 mm.
Porto Rico: San Juan; Mayaguez; Ponce; Puerto Real; Boqueron Bay;
Boca de Cangrejos; Loiza Vicja; Vieques.
McLEAN BIVALVE MOLLUSKS OF PORTO RICO
Chione (Chione) granulata (Gmelin)
PLATE 17, FIGURE 5
'enus granulata Gmelin (1792) Syst. Nat., Ed. 13: 3277.
This shell, also, is a typical member of the West Indian fauna. It has a
characteristic beaded surface. The concentric and radial elements of the
sculpture are about equal, which accounts for the granular or beaded
appearance. The color is light yellowish to brown. It is variously shaded
and marked with brown or purple coloration. The interior is shaded and
clouded with pink and purple.
Length 33, height 28, width 20 mm.
Porto Rico: San Juan; Ponce; Guanica; San Antonio Bridge.
Virgin Islands: Lindbergh Beach, Charlotte Amalie, St. Thomas; St.
John.
Chione (Chione) pygmaea (Lamarck)
PLATE 17, FIGURE 2
us pygmaea Lamarck (1818) Anim. s. Vert., 5: 585.
This small species is elongate-oval in shape. The sculpture is cancellate.
The radial ribs are single on the disk. The color is white, variously flecked
and spotted with brown. The dorsal border in the area of the escutcheon
has characteristic transverse stripes of purplish-brown color.
Length 15, height 10.5, width 7 mm.
Porto Rico: Quebradillas.
Virgin Islands: St. Thomas; St. John; Tortola.
Subgenus LIROPHORA Conrad
Lirophora Conrad (1863) Proc. Acad. Nat. Sci. Phila. for 1862, pp. 575, 586.
TYPE (by subsequent designation, Dall, 1902), Circomphalus (Lirophora) alhleta Conrad, = Venus latilirala
Conrad.
The sculpture is of broad concentric waves, attenuated and often con-
spicuously lamellose distally. There are radial striae. The edges of the
right nymph and the posterior left cardinal tooth have interlocking rugos-
ities.
KEY TO THE SPECIES OF SUBGENUS LIROPHORA
(1) Concentric rugae few, very large, not lamellose on the posterior slope
C. latilirala
(1') Concentric rugae numerous, not as large as in the preceding species, lamellose on
the posterior slope. C. paphia
Chione (Lirophora) latilirata (Conrad)
PLATE 17, FIGURE 7
Venus latilirala Conrad (1841) Proc. Aca. Nat. Sci. Phila., 1: 28.
Venus varicosa Sowerby (1853) Thes. Conch., 2: 723, PI. 155, fig. 67.
The tremendously developed concentric waves of sculpture are char-
SCIENTIFIC SURVEY OF PORTO RICO
acteristic of this species, and no other species in the West Indian region can
be confused with it.
Length 33, height 29, width 22 mm.
Porto Rico: Mayaguez.
Chione (Lirophora) paphia (Linnaeus)
PLATE 17, FIGURE 9
Venus paphia Linnaeus (1767) Syst. Nat., Ed. 12: 1129.
The concentric waves are strongly developed in this species. They are
somewhat lamellose on the anterior border and very much attenuate and
lamellose posteriorly. The color is white, more or less mottled and shaded
with reddish brown.
Length 45, height 37, width 26 mm.
Porto Rico: Mayaguez; Vieques.
Virgin Islands: St. Thomas; St. Croix; Caneel Bay, St. John; Tortola;
Virgin Gorda.
Genus ANOMALOCARDIA Schumacher
Anomalocardia Schumacher (1817) Essai Nouv. Syst. Vers Test., pp. 44, 134.
TYPE (by monotypy), Anomalocardia rugosa Schumacher, = Venus flexuosa Linnaeus.
The valves are rostrate. Their inner margins are crenulate. The liga-
ment is exposed, and the lunule and escutcheon are impressed. There are
three simple cardinal teeth in each valve. They diverge rather widely
from their common center beneath the umbones. The anterior right cardi-
nal is feeble and sometimes nearly obsolete. The pallial sinus is small,
angular, and sometimes nearly obsolete.
This group is not very markedly different from Chione. However, the
species which are placed here are all rather uniform and similar, and it is
generally regarded as a separate genus.
KEY TO THE SPECIES OF ANOMALOCARDIA
(1) Shell large and heavy. A. brasiliana
(1') Shell small and thin ..... .2
(2) Concentric ridges moderately wide and moderately spaced, 13 to 18 in number
A. puella
(2') Concentric ridges narrow and close together, 23 or more in number
A. membranula
Anomalocardia brasiliana (Gmelin)
PLATE 17, FIGURE 10
Venusflexuosa Born (1780) Test. Mus. Caes. Vind., p. 62, pl. 4, fig. 10; not Linnaeus (1767).
Venus brasiliana Gmelin (1792) Syst. Nat., Ed. 13: 3289.
Cytherea macrodon Lamarck (1818) Anim. s. Vert., 5: 580.
This heavy, corrugated species is of a yellowish-white color, variously
shaded and spotted with purple or brown. The inner margins of the valves
are crenulated. The concentric ridges are sometimes obscured on the
disk.
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Length 33, height 28, width 20 mm.
Porto Rico: San Juan; Mayaguez; Ponce; Guanica; Humacao Playa;
Boca de Cangrejos; Loiza Vieja.
Anomalocardia puella (Pfeiffer)
PLATE 17, FIGURE 6
Venus puella Pfeiffer (1846) (in] Philippi, Abb. Conch., 2 (4): 108.
'Venus auberiana d'Orbigny, 1846, Moll. Cubana, 2: 319, PI. 26, figs. 35-37.
This species, and the following one as well, may prove to be ecological
variants of A. cuneimeris Conrad, which is common in the southeastern
United States. At this time it seems best to regard them as separate.
The ranges do not overlap.
The shell is small and fragile, with 13 to 18 narrow concentric ridges.
It may be white, brown, or blue, and is variously marked or spotted with
brown.
Length 17, height 11.5, width 7.5 mm.
Virgin Islands: St. Thomas; St. Croix.
Anomalocardia membranula Rdmer
PLATE 17, FIGURE 8
Anomalocardia mcmbransda R6mer (1860) Malac. Blitt., 7: 163.
This species is characterized by the numerous fine ridges. They number
23 or more and are very closely spaced. The shell is markedly elongate
and attenuate posteriorly. The color is variable. It may be white, reddish,
or bluish, and may be shaded or marked with reddish brown.
Length 14.5, height 9, width 7 mm.
Virgin Islands: St. Thomas.
Family PETRICOLIDAE
The valves, when not distorted, are equal, free, and somewhat gaping
behind. They are radially sculptured with plain margins and inconspicuous
beaks. The posterior adductor scar is larger than the anterior one. The
pallial line is sinuated. The ligament and resilium are external. The
area is obscure or not defined. The hinge is without lateral laminae.
There are two or three small, usually bifid, radial cardial teeth in each
valve. The siphons are long, united only near the base. The outer
reflected limb of the gill has an appendix.
KEY TO THE GENERA OF PETRICOLIDAE
(1) Sculpture divaricate or zigzag. .Naranio
(1') Sculpture not divaricate or zigzag . .2
(2) Cardinal teeth closely grouped; radial sculpture predominant. .Petricola
(2') Posterior cardinal extended along the hinge line, resembling a lateral; sculpture
having radial threads and periodic concentric ridges.. Coralliophaga
Genus PETRICOLA
Petricola Lamarck (1801) Syst. Anim. s. Vert., p. 121.
TYPE (by subsequent designation, Gray, 1847), Venus tithopkagus Retzius.
SCIENTIFIC SURVEY OF PORTO RICO
The shell is inflated and rounded in front, attenuated and compressed
behind. The sculpture is chiefly radial and is stronger on the posterior
end.
Petricola typica (Jonas)
PLATE 18, FIGURE 2
Choristaodon typicum Jonas (1844) Zeitschr. Mal., : 185.
This species has the shell rounded in front and more or less compressed
and attenuate behind. The numerous radial ribs are sharp and clearly
marked off, with relatively broad interspaces. Like many burrowing spe-
cies, it is variable in shell shape. The shell color is grayish white, stained
internally with buff or brown.
Length 33, height 22, width 16 mm.
Virgin Islands: St. Thomas.
Genus NARANIO Gray
Saranio Gray (1853) Ann. Mag. Nat. Hist. (2), 11: 38.
TYPE (by subsequent designation, Dall, 1900), Naranio costata [Lamarck] Gray: Venus lapicida Gmelin.
The shell is ovate. There is a short, moderately wide pallial sinus.
The sculpture is radial and more or less divaricate or zigzag.
Naranlo lapicida (Gmelin)
PLATE 18, FIGURES 3, 4
Venus lapicida Gmelin (1792) Syst. Nat., Ed. 13: 3269.
PeJricola costaia Lamarck (1801) Syst. Animn. s. Vert., p. 121.
Pelricola divaricata d'Orbigny (1846) Moll. Cubana, 2: 311.
In this species the shell is tumid and rounded-oval, and the umbones are
well forward. The divaricating sculpture is very fine and quite distinct.
At first glance there may appear to be a pronounced radial ribbing, particu-
larly on the posterior slope of the shell. Upon careful examination it will be
seen that this is not sculpture on the true surface of the shell, but is part of
a calcareous coating which has been deposited on the shell and elaborated
to s mulate shell sculpture.
Length 29.5, height 22, width 16 mm.
Porto Rico: San Juan.
Virgin Islands: St. Thomas.
Genus CORALLIOPHAGA Blainville
Coralliophaga Blainville (1824) Dict. Sci. Nat., 32: 3.13.
TYPE (by monotypy), Coralliophaga carditoidea Blainville Charna coralliophaga Gmelin.
The shell is elongate, rounded-rectangular, and the umbones are at the
anterior end. There are three teeth in each valve. The posterior one is
extended along the hinge line like a lateral. The posterior muscle scar is
considerably larger than the anterior one. The pallial sinus is short and
angular.
This genus is tentatively included under the Petricolidae, where it was
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
placed by Johnson.' Its systematic position is uncertain. The hinge
bears three teeth in each valve. These have been regarded as three cardi-
nals by some authors, while others considered them as two cardinals and a
lateral. Dall held the latter view and placed the genus in his family
Pleurophoridae. There is disagreement in the interpretations of the ana-
tomical features of this group. The present work does not attempt to
resolve them but follows Johnson's placement of the genus.
Coralliophaga coralliophaga (Gmelin)
PLATE 18, FIGURE 1
Chama coralliophaga Gmelin (1792) Syst. Nat Ed 13: 3305.
The shell is variable in this species, depending on the habitat of the
individual. It is fundamentally elongate rounded-rectangular, but may
be narrow and elongate or quite short and rounded. The radial elements
of the sculpture are fine and threadlike. There are periodic concentric
elevated ridges with rather wide interspaces.
These animals are sometimes found in burrows which were apparently
excavated by other species. Such animals are apt to be deformed to a
greater or less degree. Others are found in holes which seem to be of their
own excavation.
Length 52, height 23, width 20 mm.
Porto Rico: Puerto Real.
Virgin Islands: St. Thomas.
Superfamily TELLINACEA
The hinge plate is narrow to moderate in thickness. There are two
cardinals in each valve. The anterior cardinal is often bifid and somewhat
pedunculate. The posterior one is frequently obsolete. Typically there
is an anterior and a posterior lateral in each valve but one or both sets may
be obsolete. The ligament is external, and the resilium is marginal or
submarginal. The pallial sinus is well marked. It is largely contiguous
with the pallial line ventrally. The adductor muscle scars are rounded.
The anterior scar is somewhat larger than the posterior one. The gills
are small or medium-sized and smooth or plicate. They are united behind
the foot. The palps are moderate to large in size. The foot is compressed
and not grooved, often short. There is no byssus. The lobes of the
mantle are free ventrally. The siphons are produced, usually long and
separate.
KEY TO THE FAMILIES OF TELLINACEA
(1) Resilium marginal or submarginal, not internal .2
(1') Resilium internal, seated on oblique chondrophores. .Semelidae
(2) Valves equal and subtrigonal, usually closed and solid; hinge plate moderately
developed. .. .Donacidae
(2') Valves slightly unequal, thin and compressed, hinge plate very narrow .3
(3) Valves slightly unequal, twisted posteriorly; epidermis inconspicuous; gills small
and palps very large. ............... Tellinidae
5 Johnson, C. W., Proc. Boston Soc. Nat. Hist. 40 (1): 50. 1934.
SCIENTIFIC SURVEY OF PORTO RICO
(3') Valves more equal and less twisted than in 3; the epidermis relatively more con-
spicuous; gills larger in proportion, and palps relatively smaller
Sanguinolariidae
Family TELLINIDAE
The shell substance is cellulo-crystalline with an inconspicuous epidermis.
The valves are compressed and slightly unequal. They are rounded in
front, more or less rostrate, oblique, and gaping behind. The valve mar-
gins are usually smooth. The beaks are low and variable in position. The
sculpture is chiefly concentric. The anterior adductor scar is larger than
the posterior one and frequently irregular. The pedal scar is distinct.
The resilium is submarginal and embraced in the ligament. The area is
narrow or obsolete. The hinge plate is narrow, with the anterior lateral
close to the cardinals and the posterior one more distant. Both laterals
may be obsolete. The cardinal teeth are small. The gills are very small
and have the outer limb dorsally directed. It is sometimes without a
reflected lamina and may be obsolete. The palps are very large and are
united behind. Anteriorly they sometimes have an antennalike projection.
The foot is sometimes capable of being flattened for use as a fulcrum. The
mantle margins are duplex, with papillose edges. The siphons are long,
unequal, and naked. They are retractile and have papillose orifices. There
is no curtain valve in the branchial siphon. The pallial sinus is deep and
discrepant in the opposite valves.
KEY TO THE GENERA OF TELLINIDAE
(1) Hinge with lateral teeth. .2
(1') Hinge without lateral teeth. .... 3
(2) Shell without oblique sculpture, or, if oblique lines are present, then shell shape
elongate Tellina
(2') Shell subcircular, with finely incised oblique sculpture crossing the concentric
growth lines. ..... Strigilla
(3) Shell with a posterior flexure but no sulcus .Macoma
(3') Shell with a posterior flexure and a large sulcus. A polymetis
Genus TELLINA Linnaeus
Tellina Linnaeus (1758) Syst. Nat., Ed. 10: 674.
TYPE (by subsequent designation, Children, 1823), Tellina radiata Linnaeus.
The shell is subequivalve, rather compressed, suborbicular or transversely
elongate, and obliquely flexed behind. The umbones are subcentral. The
hinge has two cardinals and generally two laterals in each valve. There is
one anterior and one posterior lateral, most distinct in the right valve and
often obsolete or absent in the left. The pallial sinus is wide and deep.
The ligament is external and prominent.
KEY TO TIlE SUBGENERA OF TELLINA
(1) Hinge with two lateral laminate in each valve... .Tellina s.s.
(1') Hinge with less than two lateral laminae per valve. .. 2
(2) Hinge with two lateral laminae in the right valve, the laminae of the left valve
more or less obsolete or absent ........... ................... 3
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
(2') Hinge with a strong right anterior lateral, closely adjacent to the cardinals, the
other laterals absent. .Angulus
(3) Shell greater than 10 nmm. in length. .Arcopagia
(3') Shell less than 10 mm. in length.. Moerella
Subgenus TELLINA s.s.
The characters of the subgenus are those given for the genus, with the
limiting features of the key.
KEY TO THE SPECIES OF TELLINA S.S.
(1) Shell elongate. .2
(1') Shell rather bluntly oval. .3
(2) Shell highly polished. T. radiata
(2') Shell with rough concentric sculpture. T. alternala
(3) Shell large; rounded. T, laevigata
(3') Shell small; oval. T. lineata
Telllina (Tellina) radiata Linnaeus
PLATE 18, FIGURE 5
Tellina radiata Linnaeus (1758) Syst. Nat., Ed. 10: 675.
Tellina unimaculata Lamarck (1818) Anim. s. Vert., 5: 521.
This large, elongate, highly polished species is very striking in appearance.
The shell is a pure milky white. There is some yellow shading and it is
variously rayed with pink or red coloration. The color form described by
Lamarck as unimaculata is entirely white and yellow except for a red ray
which covers the umbones and extends a short distance toward the ventral
border.
Length 114, height 53, width 27.5 mm.
Porto Rico: San Juan; Aguadilla.
Virgin Islands: Bird Key, St. Thomas; St. Croix; Cancel Bay, St. John;
Tortola; Virgin Gorda.
Tellina (Tellina) Interrupta Wood
PLATE 18, FIGURE 7
Tellina inlerrupia Wood (1815) Gen. Conch., p. 146.
Tellina antonii Philippi (1844) Abb. Conch., 1 (5): 124.
The shell is elongate and somewhat attenuate behind. The concentric
ridges are clear-cut and prominent. The color is yellowish white, variously
flecked and rayed with brown or brownish purple coloration.
Length 90, height 46, width 22 mm.
Virgin Islands: St. Thomas; St. Croix; Tortola; Virgin Gorda.
Tellina (Tellina) laevigata Linnaeus
PLATE 18, FIGURE 9
Tellina laevigaa Linnaeus (1758) Syst. Nat., Ed. 10: 675.
This large rounded species is white, with variable shading of yellow or
salmon color. The coloration is principally in the form of bands which are
concentrically arranged and irregularly spaced. Frequently the color is
SCIENTIFIC SURVEY' OF PORTO RICO
confined to the marginal part of the shell. The surface is smooth or has
inconspicuous growth lines.
Length 74, height 58, width 20 mm.
Virgin Islands: St. Thomas; St. Croix.
Tellina (Tellina) lineata Turton
PLATE 18, FIGURE 6
Tellina lineala Turton (1819) Conch. Dict., p. 168, P). 4, fig. 16.
This is a smaller species than the three preceding ones. The surface has
an indistinct concentric sculpture. The shell is more or less elongate-oval,
somewhat attenuate behind. The color is white, often with a red flush
on the umbones which extends part of the way down onto the disk.
Length 30, height 20, width 7 mm.
Porto Rico: Mayaguez.
Virgin Islands: St. Thomas.
Subgenus ARCOPAGIA Brown
Arcopagia Brown (1827) III. Conch. Great Britain and Ireland, Pl. 16, species 8.
TYPE (by subsequent designation, Herrmannsen, 18461, Tellina crassa Pennant.
The shell is compressed. It may be elongate or short and rounded.
In some sections the pallial sinus is confluent with the pallial line, while in
others it is partly free and ascending. Most of the sections have either
internal strengthening rays or a left anterior lateral tooth. There are two
cardinals in each valve.
The systematics of the Tellinidae as a whole and of this group in particular
are somewhat unsatisfactory at the present time. The lines of demarcation
between the groups are very tenuous. A careful analysis of the morpho-
logical features was made by Dall, but the uncertainty was not entirely
eliminated. Experimental investigation of the nature of the diagnostic
characters will probably have to be made before the species can be properly
grouped and correlated.
KEY TO THE SPECIES OF SUBGENUS ARCOPAGIA
(1) Shell short and rounded. .2
(1') Shell elongate. .3
(2) Shell large; surface sculptured with growth lines. T.fausta
(2') Shell small; surface with distinct concentric ridges. T. lintea
(3) Length greater than 30 mm.. .4
(3') Length less than 30 mm.. .5
(4) Concentric sculpture distinct and regular T. allernata
(4') Concentric sculpture indistinct and irregular T. angulosa
(5) Shell about 10 mm. in length. T vespuciana
(5') Shell about 20 mm. in length .6
(6) Posterior end of shell relatively short; shell suffused with apricot-yellow coloration
T persica
(6') Posterior end of shell relatively elongate; shell tinted and faintly rayed with pink
T. guildingii
McLEAN: BIVALVE MOLLUSKS OF PORTO RICO
Tellina (Arcopagla) fausta Donovan
PLATE 18, FIGURE 10
Tellina fausta Donovan (1804) Nat. Hist. British Shells, p. 10, Pl. 25, figs. 13, 14.
This large, round, smooth species is quite distinct. It is white, some-
what tinted with yellow, especially on the inside of the shell.
Length 77, height 64, width 31 mm.
Porto Rico: San Juan; Mayaguez; Ponce.
Virgin Islands: St. Thomas; St. Croix; Tortola.
Tellina (Arcopagia) llntea Conrad
PLATE 18, FIGURE 8
Tellina lindea Conrad (1837) Jour. Acad. Nat. Sci. Phila., 7: 259, Pl. 2, fig. 3.
This fine little species is distinctly concentrically sculptured. The shell
is rounded anteriorly, somewhat attenuate and strongly flexed posteriorly.
The color is white.
Length 20, height 13, width 5 mm.
Porto Rico: Mayaguez.
Tellina (Arcopagia) alternate Say
PLATE 19, FIGURE 1
Tellina alternate Say (1822) Jour. Acad. Nat. Sci. Phila., 4: 275.
Tellina layloriana Sowerby (1867) Conch. Icon., 17, PI. 30, fig. 68.
This large, elongate species has distinct and regular concentric sculpture.
It occurs in a white phase and a pink phase. The latter one has received
the name layloriana. It is apparently just a color form, but does not occur
throughout the entire range of the species. It is close to the following
species, but differs in the more regular sculpture. It is also a larger species,
and the posterior end of the shell is a little more elongate.
Length 65, height 35, width 12 mm.
Porto Rico: Mayaguez.
Virgin Islands: St. Thomas.
Tellina (Arcopagia) angulosa Gmelin
PLATE 19, FIGURE 2
Tellina angulosa Gmelin (1792) Syst. Nat., Ed. 13: 3244.
This species resembles the preceding one, but the sculpture is indistinct
and irregular and the posterior end of the shell is shorter. The height is
slightly greater in proportion to the length than in allernala, and the shell
is somewhat smaller. It almost always has some degree of pink coloration.
Length 56, height 29, width 10.5 mm.
Virgin Islands: Magens Bay, St. Thomas.
Tellina (Arcopagia) vespuciana d'Orbigny
PLATE 19, FIGURE 5
Tellina respuciana d'Orbigny (1846) Moll. Cubana, 2: 254. PI. 26, figs. 12-14.
SCIENTIFIC SURVEY OF PORTO RICO
This small, elongate species has a flexure of the posterior ends of the
valves. It is finely, regularly, concentrically sculptured. It was described
by d'Orbigny as a white shell, but Dall reports a red color phase.
Length 11, height 6.5, width 3 mm.
Porto Rico: Mayaguez.
Tellina (Arcopagla) guildingil Hanley
PLATE 19, FIGURE 7
Tellina guildingii Hanley (1844) Proc. Zool. Soc. London, 12: 60.
Tellina (Eurylellina) georgiana Dall (1900) Proc. U. S. Nat. Mus., 23 (1210): 310, PI. 2, fig. 3; not Tellina
georgiana Gabb.
This species has the posterior end of the shell relatively elongate. The
surface is covered with a fine, regular, concentric sculpture. It is white,
shaded and rayed with pink, and sometimes tinged with yellow.
Length 17, height 10, width 4 mm.
Porto Rico: Mayaguez; Aguadilla.
Virgin Islands: St. Thomas.
Tellina (Arcopagia) persica Dall and Simpson
PLATE 19, FIGURE 3
Tellina persica Dall and Simpson (1901) Bull. U. S. Fish Comm. 20: 479, Pl. 55, fig. 1.
This species is of a very characteristic color. It is white but largely
shaded with apricot-yellow on the outside and on the inside as well. It is
somewhat less elongated posteriorly than the preceding species. The con-
centric sculpture is more prominent on the posterior slope.
Length 20.5, height 13, width 5.5 mm.
Porto Rico: Mayaguez.
Subgenus MOERELLA Fischer
laerella Fischer (1887) .Man. Conch., p. 1147.
TYPE (by monotypy), Tellina donacina Linnaeus.
The shell is elongate-ovate, inequilateral, with the posterior end ob-
scurely rostrate. The sculpture consists of concentric rugae. The right
anterior cardinal and the left posterior cardinal are very small. The right
laterals are strong, and the anterior one is closer to the cardinals than the
posterior one. The left laterals are weak, the anterior one being still weaker
than the posterior one. The pallial sinus almost touches the anterior
adductor muscle scar and is confluent with the pallial line below. Its
apex is U-shaped.
Tellina (Moerella) martinicensis d'Orbigny
PLATE 19, FIGURE 10
Telling marli iensis d'Orbigny (1846) Moll. Cubana, 2: 253, P. 26, figs. 6, 8.
This little species is quite tumid. It is more or less rostrate behind.
The surface is marked with a pronounced concentric sculpture. The shell is
white.
.HcLEAN: BIVALIE MOLLUSKS OF PORTO RICO
Length 10, height 8, width 4 mm.
Porto Rico: San Juan; Puerto Real.
Virgin Islands: Charlotte Amalie, St. Thomas.
Subgenus ANGULUS Megerle
Angulus IMegerle (1811) Ges. Nat. Fr. Berlin Mag., 5 (1): 47.
TYPE (by subsequent designation, Gray, 1847), Tellina lanceolala Grnelin.
The shell is elongated, variable in size, but chiefly small and compressed.
The posterior end is angularly pointed but not twisted. The surface is
smooth or finely concentrically sculptured. There are two cardinal teeth
in each valve. There is a strong right anterior lateral closely adjacent to
the cardinals. The left laterals are absent, and the posterior right lateral
is obsolete. The valves are occasionally strengthened -with thickened in-
ternal rays.
KEY TO THE SPECIES OF SUBGENUS ANGULUS
(1) Surface smooth or with fine concentric striation. .. .2
(1') Surface having fine oblique grooves crossing the concentric sculpture at an angle
8
(2) Shell very large. T. magna
(2') Shell small. .3
(3) Shell short, rounded. T promera
(3') Shell elongate. .4
(4) Ventral border more or less straight. .5
(4') Ventral border smoothly rounded. .T. vitrea
(5) Posterior end of shell rather blunt. .6
(5') Posterior end of shell relatively angular .7
(6) Posterior end of shell somewhat more elongate than the next species; shell faintly
rayed with red. T. consobrina
(6') Posterior end of shell very short and obtuse; shell color white. .T pauperala
(7) Posterior end of shell produced but rounded at the tip; shell color white
T, simplex
(7') Posterior end of shell produced but truncate squarely at the tip; shell red, colora-
tion intensified in concentric waves. T. sybaritica
(8) Posterior end of shell nearly as long as anterior end. T. caribaea
(8') Posterior end of shell very short. T. candeana
Tellina (Angulus) magna Spengler
PLATE 19, FIGURE 12
Tellina magna Spengler (1798) Skr. Nat. Selsk. Copenhagen, 4 (2): 76.
This large, oval, compressed species is smooth except for some indistinct
radial striation near the margin. It is white or concentrically shaded with
pink or orange. It is quite distinct.
Length 108, height 63, width 19 mm.
Virgin Islands: St. Croix.
Tellina (Angulus) promera Dall
PLATE 19, FIGURE 11
Tellina (Angulus) promera Dall (1900) Proc. U. S. Nat. Mus., 23 (1210): 312, PI. 2, fig. 11.
This is a rather short species, rounded in front and bluntly angular
SCIENTIFIC SURVEY OF PORTO RICO
behind. The surface has low, irregular, concentric sculpture. The shell is
white.
Length 22, height 16.5, width 7 mm.
Virgin Islands: Lindbergh Beach, St. Thomas.
Tellina (Angulus) vitrea d'Orbigny
PLATE 19, FIGURE 8
Tellina vitrea d'Orbigny (1846) Moll. Cubana, 2: 253, Pl. 26, figs. 4, 5.
This thin, glassy little species has a rather distinctive shape. The ven-
tral border of the valves is smoothly curved, causing the shell to appear
more or less pointed at each end. The surface is smooth with very fine
concentric lines. The color is translucent white.
Length 33, height 18, width 6 mm.
Porto Rico: Mayaguez; Boqueron Bay.
Tellina (Angulus) consobrina d'Orbigny
PLATE 19, FIGURE 9
Tellina consobrina d'Orbigny (1846) Moll. Cubana, 2: 254, Pl. 26, figs. 9-11.
This shell was mentioned by d'Orbigny as having certain resemblances
to the much larger T radiata. It is elongate-oval in shape and sculptured
with fine concentric lines. The shell is thin. It is white with yellow tinting
and rays of pink coloration.
Length 15, height 8, width 4 mm.
Porto Rico: Mayaguez.
Virgin Islands: St. Thomas.
Tellina (Angulus) pauperata d'Orbigny
PLATE 19, FIGURE 6
Telling pauperata d'Orbigny (1846) Moll. Cubana, 2: 306, Pl. 26, figs. 18-20.
This little white species is nearly smooth on the surface. There are
fine concentric growth lines. The posterior end is characteristically short
and truncated in appearance.
Tellina (Angulus) simplex d'Orbigny
PLATE 19, FIGURE 4
Tellina simplex d'Orbigny (1846) Moll. Cubana. 2: 305, PI. 26, fig,.
This little, smooth, white species resembles the preceding one and the
following one as well. It may be distinguished from the former by its
more attenuate posterior end, and from the latter by the absence of strong
pink coloration.
Length 10.5, height 6, width 3 mm.
Virgin Islands: St. Thomas.
Tellina (Anbulus) sybaritica Dall
PLATE 20, FIGURE I
Tellina sybarilica Dall (1881) Bull. Mus. Comp. Zobl., 9:
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