diverging summits, strongly flexed anteriorly and outwardly, in a
commencing spiral, hinge dorsal, long, similar, formed of two flat
cardinal teeth and one lamellous behind the ligament; ligament dorsal,
exterior, diverging anteriorly towards the summit; muscular impressions
very distant and small. Inhabits the Mediterranean and British seas.
Four living species. One fossil.
Isocardia Moltikana.
I. retusum.
I. cor.
I. semisulcata.
FAMILY XI.
ARCACEA. Four Genera.
1. Genus _Arca_. Pl. VIII.
_Animal._ Body thick, slightly variable in form; abdomen provided with a
pedunculated foot, compressed, fit for adhesion, and cleft throughout
its extent; mantle supplied with a simple row of cirri and slightly
prolonged posteriorly; buccal tentacula very small and very thin.
_Shell._ Somewhat diversiform, but most usually elongated and more or
less oblique at the posterior extremity, often very inequilateral;
summits more or less distant and little flexed to the front; hinge
anomalous, straight, or a little flexed, long, and formed by a line of
short vertical teeth, decreasing from the extremities to the centre;
ligament exterior, wide, nearly as much before as behind the summit; two
muscular impressions united by a band or palleal impression, not very
distinct. Inhabits the American and British seas. Forty-one living
species. Nine fossil.
Arca semitorta.
A. tetragona.
A. sinuata.
A. cardissa.
A. retusa.
A. ovata.
A. scapha.
A. fusca.
A. Domingensis.
A. trapezina.
A. inequivalvis.
A. tortuosa.
A. Noæ.
A. umbonata.
A. avellana.
A. ventricosa.
A. sulcata.
A. Helbingii.
A. barbata.
A. Magellanica.
A. pisolina.
A. callifera.
A. bisulcata.
A. senilis.
A. auriculata.
A. Cayennensis.
A. antiquata.
A. Braziliana.
A. lactea.
A. cancellaria.
A. irudina.
A. rhombea.
A. corbicula.
A. Indica.
A. granosa.
A. squamosa.
A. pistachia.
· · · · ·
A. ponderosa.*
A. pexata.*
A. incongrua.*
A. transversa.*
2. Genus _Cucullæa_. Pl. VIII.
_Animal._ As above.
_Shell._ Trapeziform, inequilateral, equivalve, heart-shaped; beaks far
apart, separated by the angular groove of the ligament, which is
altogether external; hinge linear, straight, with small transverse
teeth, having at its extremity from two to five parallel ribs; valves
minutely striated longitudinally; margins crenulated. The Cucullæa is
distinguished from the Arca by the muscular impression, to one side of
which is an auriform testaceous appendage; the shell also is more
trapeziform. Inhabits the Indian ocean. One living species. One fossil.
Cucullæa auriculifera.
3. Genus _Pectunculus_. Pl. VIII.
_Animal._ Body round, more or less compressed; mantle without cirri or
tubes; foot securiform, cleft at its inferior anterior edge; buccal
appendages linear.
_Shell._ Orbicular, equivalve, subequilateral; summit nearly vertical,
and more or less distant; hinge formed upon each valve, of a numerous
series of small teeth disposed in a curved line, sometimes interrupted
beneath the summit; ligament as in Arca, but usually much narrower.
Inhabits the British and Mediterranean seas. Twenty-two living species.
Nine fossil.
Pectunculus pilosus.
P. marmoratus.
P. Pennaceus.
P. castaneus.
P. angulatus.
P. palleus.
P. zonalis.
P. glycimeris.
P. undulatus.
P. scriptus.
P. stellatus.
P. violacescens.
P. aggregatus.
P. striatularis.
P. pectinatus.
P. rubeus.
P. pectiniformis.
P. nummarius.
P. radiatus.
P. vitreus.
P. inscriptus.
P. cinerosus.
4. Genus _Nucula_. Pl. VIII.
_Animal._ Body subtriquetral; mantle open in its inferior half only,
with whole edges, denticulated throughout the extent of the back,
without posterior prolongation; foot very large, thin at the root,
enlarged into a wide oval disk, the edges of which are furnished with
tentacular digitations; anterior buccal appendages, pretty long,
pointed, stiff, and applied one against the other like jaws; the
posterior ones also stiff and vertical.
_Shell._ More or less thick, subtriquetral, equivalved, inequilateral,
with summits contiguous and inclined anteriorly; hinge similar, formed
by a numerous series of very sharp teeth, pectinated and arranged in a
line interrupted under the summit; ligament internal, short, inserted in
a little oblique pit in each valve; two muscular impressions. Inhabits
the British and American seas. Forty-five living species. Four fossil.
Nucula lanceolata.
N. pella.
N. obliqua.
N. elongata.
N. tellinoides.
N. crenifera.
N. Arctica.
N. curvirostra.
N. glacialis.
N. fluviatilis.
N. minuta.
N. para.
N. Mauritania.
N. rostrata.
N. Nicobarica.
N. Margaritacea.
N. Costellata.
N. gibbosa.
N. eburnea.
N. polita.
N. nasuta.
N. fabula.
N. Elenensis.
N. cuneata.
N. striata.
N. rugulosa.
N. Limatula.
N. lævis.
N. concentrica.
N. decussata.
N. exigua.
N. squamosa.
N. gigantea.
N. nitida.
N. tenuis.
N. convexa.
N. Pisum.
N. carinifera.
N. torta.
N. plicaria.
· · · · ·
N. navicularis.*
N. tenuisulta.*
N. proxima.*
N. acuta.*
N. myalis.*
FAMILY XII.
TRIGONACEA. Two genera.
1. Genus _Trigonia_. Pl. VIII.
_Animal._ Entirely unknown.
_Shell._ Subtrigonal or suborbicular, thick, regular, equivalve,
inequilateral; summits but slightly prominent, little flexed,
anterodorsal; hinge complex, dorsal, dissimilar; two thick oblong teeth
joined angularly under the summit, strongly furrowed upon the right
valve, penetrating into two excavations of the same form, also furrowed,
in the left valve; ligament postapicial; two distinct muscular
impressions, not united by a band. Inhabits the Australian seas. One
living species. Fifteen fossil.
Trigonia pectinata.
2. Genus _Castalia_. Pl. VIII.
_Animal._ Body large, slightly compressed, or moderately thick, more or
less oval; mantle with thick edges, simple or broken, open in all its
circumference except towards the back a kind of small, incomplete tube,
furnished with two rows of somewhat elongated cirri for the respiratory
cavity; flamelliform and trenchant.
_Shell._ Subtrigonal, equivalve, inequilateral; umbones eroded, covered
with epidermis, and flexed anteriorly; hinge with two lamellar teeth
transversely striated, one distant, posterior and shortened, the other
anterior, long, and lateral; ligament exterior. Habitation unknown. One
species.
Castalia ambigua.
FAMILY XIII.
NAIADEA. Four genera.
1. Genus _Unio_. Pl. VIII.
_Animal._ See _Castalia_.
_Shell._ Usually very thick, nacred within, covered with epidermis,
corroded at the summits, which are dorsal and subanterior; dorsal hinge
formed by a double precardinal tooth, more or less compressed,
irregularly dentated on the left valve, and simple on the right,
together with a long lamellous tooth under the ligament: ligament
external, dorsal, and postapicial; two muscular impressions, well
marked, besides those of the retractile muscles. The species of this
genus grow more numerous daily; they are found in all countries, but
particularly in North America. One hundred and sixty-seven defined
species. Numerous fossil.
Unio Batayus.
U. crassissimus.
U. elongatus.
U. litoralis.
U. pictorum.
U. platyrhynchus.
U. marginalis.
U. tigris.
U. Egyptiacus.
U. Niloticus.
U. Leaii.
U. crassidens.
U. obliquus.
U. plicatus.
U. purpuratus.
U. radiatus.
U. rectus.
U. retusus.
U. rotundatus.
U. Australis.
U. Nova Hollandica.
The following species are American:
Unio Bengalensis. _Lea._
U. bilineatus. „
U. lamellatus. _Lea._
U. Morchisonianus. „
U. cæruleus. _Lea._
U. corrugatus. „
U. Corrianus. „
U. Graianus. „
U. alatus. „
U. andontoides. „
U. Augustatus. „
U. apiculatus. „
U. arcæformis. „
U. arctior. „
U. asperimus. „
U. asper. „
U. Blandingianus. „
U. Barnesianus. „
U. brevidens. „
U. camelus. „
U. capsæformis. „
U. carbonarius. „
U. castanus. „
U. Claibornensis. „
U. circulus. „
U. occineus. „
U. compressus. „
U. complanatus. „
U. confertus. „
U. congaræus. „
U. contradens. „
U. Cooperianus. „
U. creperus. „
U. cuprinus. „
U. Cumberlandicus. „
U. decisus. „
U. dolabriformis. „
U. donaciformis. „
U. Dorfeuillianus. „
U. uromas. „
U. ebenus. „
U. elegans. „
U. olivarus. _Lea._
U. ponderosus. „
U. divaricatus. „
U. acutissimus. „
U. fabalis. „
U. Fisherianus. „
U. folliculatus. „
U. fulvus. „
U. gibber. „
U. glaber. „
U. glans. „
U. globosus. „
U. graniferus. „
U. Griffithianus. „
U. Haysianus. „
U. heterodon. „
U. Hildrethianus. „
U. Hopetonensis. „
U. Hydianus. „
U. inflatus. „
U. interruptus. „
U. iris. „
U. irroratus. „
U. Jayensis. „
U. jegunus. „
U. Katherinæ. „
U. Kirklandianus. „
U. lævissimus. „
U. lacrymosus. „
U. lancolatus. „
U. Lecontianus. „
U. lens. „
U. lugubris. „
U. luteolus. „
U. Medellinus. „
U. Menkianus. „
U. metanever. „
U. Mühlfeldianus. „
U. ellipsis. _Lea._
U. multiradiatus. „
U. modiolioformis. „
U. notatus. „
U. Novi-Eboraci. „
U. obesus. „
U. obscurus. „
U. occidens. „
U. palliatus. „
U. patulus. „
U. stapes. „
U. perdix. „
U. perplexus. „
U. pictus. „
U. pileus. „
U. pliciferus. „
U. pulcher. „
U. pumilis. „
U. pustulatus. „
U. pustulosus. „
U. pyramidatus. „
U. Rangianus. „
U. Ravenelianus. „
U. Roanokensis. „
U. rubiginosus. „
U. Schoolcraftensis. „
U. securis. „
U. Shepardianus. „
U. simus. „
U. solidus. „
U. Sowerbianus. „
U. spinosus. „
U. splendidus. „
U. multiplicatus. _Lea._
U. subovatus. „
U. subrotundus. „
U. sulcatus. „
U. Taitianus. „
U. Tampicoensis. „
U. Tappanianus. „
U. tenuissimus. „
U. trapezoides. „
U. trigonus. „
U. Troostensis. „
U. turgidus. „
U. Vanuxemensis. „
U. varicosus. „
U. Vaughanianus. „
U. venustus. „
U. Watercensis. „
U. Zeiglerianus. „
U. zigzag. „
U. alatus. _Say._
U. apiculatus. „
U. camptodon. „
U. cariosus. „
U. crassus. „
U. cylindricus. „
U. declivis. „
U. dehiscens. „
U. monodontus. „
U. nasutus. „
U. ovatus. „
U. personatus. „
U. subtentus. „
U. tetralasmus. „
2. Genus _Hyria_. Pl. VIII.
_Animal._ As above.
_Shell._ Solid, nacred, equivalve, obliquely triangular, auriculated;
base straight and truncated; hinge with two projecting teeth, the
cardinal divided into numerous radiations, anterior ones smaller, the
others lamellar and long. Inhabits the lakes and rivers of America. Two
species.
Hyria avicularis.*
Hyria corrugata.*
NOTE.—_Alasmidonta._ Separated by Say from the Anodonta by its primary
tooth, and from the Unio by being destitute of the lamelliform teeth.
_Shell._ Transverse, equivalve, inequilateral; hinge with a primary
tooth in each valve; cicatrices three. Four species.
Alasmidonta undulata.
A. ambigua.
A. marginata.
A. confragosa.
3. Genus _Anodonta_. Pl. VIII.
_Animal._ As above.
_Shell._ Rather thin, regular, close, equivalve, inequilateral; summit
anterodorsal; hinge entirely without teeth, with a postapicial lamina;
ligament external, dorsal, and postapicial, two well marked muscular
impressions, besides those of the retractile muscles. Inhabits
fresh-water lakes in Europe and America. Forty-nine living species; and
many fossil.
Anodonta areolatus.
A. marginata.
A. rubens.
A. anatina.
A. fragilis.
A. trapezialis.
A. rufa.
A. uniopsis.
A. intermedia.
A. glauca.
A. anatina.
A. sinuosa.
A. Patagonica.
A. cygnæa.
A. sulcata.
A. cataracta.
A. exotica.
A. crispata.
A. Pennsylvanica.
A. maximus.
The following species are American.
Anodonta magnifica. _Lea._
A. Woodiana. „
A. angulata. „
A. Benedictensis. „
A. cylindracea. „
A. decora. „
A. edentula. „
Anodonta gigantea. _Lea._
A. incerta. „
A. Pepiniana. „
A. plana. „
A. salmonia. „
A. Stewartiana. „
A. subcylindracea. „
A. Ferussacina. _Lea._
A. fluviatilis. „
A. Newtonensis. „
A. Nuttalliana. „
A. Oregonensis. „
A. ovata. „
A. pavonia. „
A. Wahlamatensis. „
A. Wardiana. „
A. gibbosa. _Say._
A. grandis. „
A. impura. „
A. suborbiculata. „
A. undulata. „
A. lugubris. „
4. Genus _Iridina_. Pl. VIII.
_Animal._ As above.
The principal difference between the Anodonta and the Iridina, consists
in the tuberculated hinge of the latter.
_Shell._ Thin, oval, much elongated, inauriculated; hinge very long,
linear, and crenulated throughout its length, ligament external and
marginal; two distinct muscular impressions. Inhabits the Nile and
American coasts. Six species.
Iridina exotica.
I. Nilotica.
· · · · ·
I. cælistis.*
I. rubens.*
I. elongata.*
I. McMurtria.*
FAMILY XIV.
CHAMACEA. Three genera.
1. Genus _Diceras_. Pl. VIII.
_Animal._
_Shell._ Inequivalve, adherent; beaks conical, very large, diverging in
irregular spiral contortions; hinge with a large, thick, concave,
subauricular tooth in the larger prominent valve; two muscular
impressions. One species. Fossil.
Diceras arietina.
2. Genus _Chama_. Pl. VIII.
_Animal._ Body suborbicular terminated superiorly by a sort of hook;
mantle very slightly opened for the passage of a foot, terminated at its
extremity by a part much narrower than the base; superior lobes of the
branchiæ very short.
_Shell._ Irregular, adhering, inequivalve, inequilateral; summits more
or less twisted spirally, especially in the lower valve by which these
animals have the faculty of affixing themselves to other bodies; hinge
dissimilar, thick, formed by a single lamellous tooth arcuated,
subcrenulated, postcardinal and articulated in a furrow of the same
form; ligament anterior and postapicial; two large muscular impressions,
distant. British and American seas. Eighteen living species.
Chama damæcornis.
C. crenulata.
C. arcinella.
C. cristella.
C. Lazarus.
C. gryphoides.
C. unicornis.
C. radians.
C. æruginosa.
C. decussata.
C. ruderalis.
C. Japonica.
C. limbula.
C. asperella.
C. albida.
C. croceata.
· · · · ·
C. exogyra.*
C. Florida.*
3. Genus _Etheria_. Pl. VIII.
_Animal._ Unknown.
_Shell._ Adhering, irregular, thick, much nacred, inequilateral,
inequivalve; summits subcephalic, thick, indistinct, in a species of
heel, growing longer with age; hinge without teeth, callous, irregular
and thick; ligament subdorsal in the exterior portion of the shell, and
prolonged to a point internally; two irregular oblong muscular
impressions, one superior and subposterior, the other inferior and
anterior, with a marginal palleal impression. Inhabits the Indian Ocean.
Five species.
Etheria elliptica.
E. trigonula.
E. semilunata.
E. transversa.
E. Carteronii.
FAMILY XV.
TRIDACNEA. Two genera.
1. Genus _Tridacna_. Pl. VIII.
_Animal._ Body somewhat thick; edges inflated, lobes of the mantle
adhering, and united in nearly all their circumference, so as to present
but three apertures, the first inferior and anterior, for the egress of
the foot; the second superior and posterior for the bronchial cavity,
the third much smaller and in the middle of the dorsal edge; two pairs
of labial appendages, thin, nearly filiform, in the middle of which is a
very small buccal orifice; branchiæ long and narrow; abdominal muscular
mass considerable, and giving issue, as if from a cup, to a thick bundle
of byssoid muscular fibres.
_Shell._ Thick, solid, of variable size, regular, triangular,
inequilateral; summits inclined posteriorly, hinge dissimilar, entirely
anterior to the summit; a lamellous precardinal tooth and two distant
lateral teeth upon the left valve, corresponding with two precardinal
lamellous teeth, and one distant lateral tooth upon the right valve;
ligament anterior, elongated; a large, bifid, submedian muscular
impression; another anterior one smaller and less distinct. Inhabits the
Indian Ocean. Seven living species. One fossil.
Tridacna gigas.
T. squamosa.
T. elongata.
T. crocea.
T. mutica.
T. serrifera.
T. pustulosa.
2. Genus _Hippopus_. Pl. VIII.
_Animal._ As above.
_Shell._ More elongated and inequilateral than in the _Tridacna_, the
anterior side being longer than the posterior; the posterior slope
closed with a dentated margin. Inhabits the Indian seas. One species.
Hippopus maculatus.
FAMILY XVI.
MYTILACEA. Three genera.
1. Genus _Mytilus_. Pl. VIII.
_Animal._ Body oval, somewhat inflated; mantle open in its inferior half
only, and terminated posteriorly by an oval cleft with fringed edges; a
linguiform, canaliculated, abdominal appendage, with a byssus at its
base behind, and several pairs of retractile muscles; mouth with simple
lips; two contractile muscles, of which the anterior is very small.
_Shell._ Of a serrated tissue, elongated, more or less oval, sometimes
subtriangular, equivalve, summits anterior, more or less curved, sloping
inferiorly in a slight degree; hinge toothless, or with two very small
rudiments; ligament dorsal, linear, subinterior, inserted in a narrow
and very long furrow; two muscular impressions, of which the anterior is
very small, besides those of the retractile muscles. Inhabits the
British and American seas. Forty-two species.
Mytilus erosus.
M. decussatus.
M. elongatus.
M. Zonarius.
M. violaceus.
M. smaragdinus.
M. edulis.
M. Hesperianus.
M. exustus.
M. ovalis.
M. Domingensis.
M. Afer.
M. ungularis.
M. borealis.
M. augustanus.
M. lacunatus.
M. incurvatus.
M. abbreviatus.
M. Magellicanus.
M. crenatus.
M. hirsutus.
M. latus.
M. ungulatus.
M. opalus.
M. corneus.
M. retusus.
M. perna.
M. bilocularis.
M. ustulatus.
M. Senegalensis.
M. achatinus.
M. planulatus.
M. Galloprovincialis.
M. lineatus.
M. canalis.
M. sanguineus.
· · · · ·
M. hamatus.*
M. croceus.*
M. cubitus.*
M. lateralis.*
M. Californianus.*
M. leucophœatus.*
2. Genus _Modiola_. Pl. VIII.
_Animal._ As above.
Separated by Lamarck from the Mytilus, on account of its being more
transverse than longitudinal, the beaks instead of being terminal are
placed beneath the apex.
_Shell._ Smooth, subtransverse, equivalve, regular, subtriangular,
posterior side short; summits nearly lateral; hinge toothless, linear
and lateral; ligament partly interior, situated in a marginal furrow;
one sublateral, elongated muscular impression in each valve. Inhabits
the British and American seas. Thirty-two species.
Modiola Guyanensis.
M. pulex.
M. discors.
M. cinnamorea.
M. plicata.
M. lithophaga.
M. Adriatica.
M. discrepans.
M. trapezina.
M. silicula.
M. semen.
M. lævigata.
M. Papuana.
M. tulipa.
M. albicosta.
M. vagina.
M. picta.
M. sulcata.
M. plicatula.
M. semifusca.
M. purpurata.
M. barbata.
M. caudigera.
M. squamosa.
M. securis.
· · · · ·
M. Americana.*
M. castanea*
M. opifex.*
M. capax.*
M. recta.*
M. Carolinensis.*
M. semi-costata.*
3. Genus _Pinna_. Pl. VIII.
_Animal._ Body oval, elongated, moderately thick, enveloped in a mantle
closed above, open below, and especially to the rear, where it forms
sometimes a sort of tube furnished with tentacular cirri: a flabelliform
abdominal appendage, and a very considerable byssus; mouth provided with
double lips, beside two pairs of labial appendages; a single large
retractile muscle apparent.
_Shell._ Subcornate, fibrous, brittle, regular, equivalve, longitudinal,
triangular, pointed anteriorly, in which direction is the summit, which
is straight, wide, and frequently truncated posteriorly; hinge dorsal,
longitudinal, linear, toothless; ligament occupying nearly all the
dorsal edge of the shell; a single and very wide muscular impression
posteriorly; a trace of the anterior in the summit. Inhabits the
Mediterranean Sea. Fifteen species.
Pinna rudis.
P. seminuda.
P. nobilis.
P. marginata.
P. pectinata.
P. ingens.
P. varicosa.
P. flabellum.
P. angustina.
P. squamosa.
P. muricata.
P. saccata.
P. dolabrata.
P. vexillum.
P. nigrina.
FAMILY XVII.
MALLEACEA. Five genera.
1. Genus _Crenatula_. Pl. VIII.
_Animal._ Unknown.
_Shell._ Irregular, much flattened, subrhomboidal, subequivalve, gaping
posteriorly; summit anterior; hinge longitudinal, dorsal, toothless;
ligament submultiple, or inflated from place to place, and inserted in a
series of round cavities corresponding with the dorsal edge; muscular
impression unique and subcentral. Inhabits the Red Sea. Seven species.
Crenatula modiolaris.
C. avicularis.
C. nigrina.
C. bicostalis.
C. viridis.
C. mytiloides.
C. phasianoptera.
2. Genus _Perna_. Pl. VIII.
_Animal._ Body much compressed, the mantle prolonged posteriorly in a
sort of lobe, and fringed at its inferior edge only; a byssus; a single
contractile muscle.
_Shell._ Irregular, much compressed, subequivalve, form somewhat
variable, gaping at the anterior part of its inferior edge; summit very
small: hinge straight, vertical, buccal, toothless; ligament multiple,
and inserted in a series of longitudinal and parallel furrows; a
subcentral muscular impression. Inhabits the Indian seas. Ten species
living. Two fossil; one found in France and one in Virginia.
Perna ephippium.
P. isognomon.
P. femoralis.
P. marsupium.
P. obliqua.
P. sulcata.
P. vulsella.
P. nuclea.
P. avicularis.
P. canina.
3. Genus _Malleus_. Pl. VIII.
_Animal._ Imperfectly known, but certainly byssiferous, with a single
retractile muscle.
_Shell._ Subnacreous, irregular, subequivalve, inequilateral, generally
much auriculated anteriorly, and prolonged posteriorly into the body, so
as to present some resemblance to a hammer; summits entirely anterior;
between them and the inferior auricle, an oblique slope for the passage
of the byssus; hinge linear, very long, buccal, toothless; ligament
simple, triangular, inserted in a conical oblique pit, partly external;
a moderately large subcentral muscular impression. Inhabits the
Australian seas. Six species.
Malleus normalis.
M. vulgaris.
M. albus.
M. vulsellatus.
M. anatinus.
M. decurtatus.
4. Genus _Avicula_. Pl. IX.
_Animal._ Body much compressed; mantle cleft throughout its
circumference, except along the back, and garnished at its free edge
with a double row of very short tentacular cirri; foot small,
canaliculated; a byssus; mouth surrounded with fringed lips, besides two
pair of labial appendages, a large contractile muscle, nearly posterior.
_Shell._ Foliaceous or not; always nacred, subequivalve, of a subregular
form, but somewhat variable; valves oblique, the left one with a little
notch, through which the byssus passes; hinge linear, toothless, or with
two small rudimentary teeth; ligament more or less exterior, placed in a
narrow groove; one very large posterior muscular impression and one very
small anterior. Inhabits the British and American coasts. Nineteen
species.
Avicula nudata.
A. macroptera.
A. semi-sagitta.
A. falcata.
A. Tarentina.
A. squamulosa.
A. Costellata.
A. lotaria.
A. heteroptera.
A. crocea.
A. Atlantica.
A. papilionacea.
A. physoides.
A. virens.
A. trigonata.
A. phalænacea.
· · · · ·
A. hirundo.*
A. pallida.*
A. nebulosa.*
5. Genus _Meleagrina_. Pl. IX.
_Animal._ As above.
_Shell._ Subequivalve, rounded, squamous, a sinus posteriorly for the
passage of the byssus, at which place the left valve is notched and
narrow; hinge linear and destitute of teeth; ligament marginal,
elongated, partly exterior, and dilated in the centre. Inhabits the
Indian Ocean. Two species, of which the first is the pearl-oyster.
Meleagrina margaritifera.
M. albina.
FAMILY XVIII.
PECTINEA. Seven genera.
1. Genus _Pedum_. Pl. IX.
_Animal._ Unknown, but probably byssiferous.
_Shell._ Subtriangular, inequilateral, inequivalve, with rounded
summits, freely marked, unequal and distant: the right valve inflated,
widened at its inferior and posterior edge, sloped anteriorly, and
subauriculated, the left not being so; hinge toothless, anterior or
buccal; ligament inserted in an oblique cavity prolonged outwardly to
the summits, and carried within into a spoon-like cavity. Inhabits the
Indian Ocean. One species.
Pedum spondyloideum.
2. Genus _Lima_. Pl. IX.
_Animal._ Body moderately compressed; a byssiferous abdominal appendage;
edges of the mantle furnished with tentacular cirri in several rows;
mouth surrounded with a very thick fringed lip.