Part 7

Shell irregular, very compressed, foliaceous, sub-equivalve, rather variable form, gaping at the anterior part of the lower extremity; summit very small, hinge straight, vertical, without teeth; ligament multiple, and inserted in a series of longitudinal parallel furrows.

Perna ephippium. P. obliqua. P. isognomon. P. avicularis. P. femoralis. P. canina. P. marsupiom. P. sulcata. P. vulsella. P. nucleus.

_P. femoralis._ The femoral Perna. Pl. 14, fig. 1.

Species elongated, and with appendages like ears.

_P. vulsella._ The tweezer Perna.

Species elongated, without earlike appendages, or having very small ones.

_P. ephippium._ The saddle Perna.

Species round, compressed, very pearly in the interior; very slightly, if at all, auricled; margin acute; exterior purplish brown.

3. Malleus. The Hammer. Six species.

A shell of a singular form, resembling a pickaxe, found only in the Indian and Australian Seas; there are two species, the white and the black, both of which, when in fine preservation, are highly esteemed, but the white is more rare and valuable.

Shell sub-nacreous, irregular, rugged, sub-equivalve, inequilateral, generally auricled before and prolonged behind, so as to be in form like a hammer; summit entirely anterior; between them and the inferior auricle, an oblique cut or slope for the passage of the byssus; hinge linear, elongated, without teeth; ligament simple, triangular, inserted in a conical oblique cavity, partly exterior; one rather large sub-central muscular impression.

Malleus albus. M. vulgaris. M. normalis. M. vulsellatus. M. anatinus. M. decurtatus.

_M. vulgaris._ The common Malleus. Pl. 14, fig. 4.

Species with two earlike appendages; trilobate, colour blackish brown.

_M. albus._ The white Malleus.

Species trilobate; base of the lateral lobe prolonged, without a sinus; the base and the pit of the ligament not distinct; colour white, with transverse undulations.

_M. vulsellatus._ The tweezer Malleus.

Species slightly auricled.

_M. normalis._ The square Malleus.

Species without earlike appendages.

4. Avicula. Thirteen species.

Remarkable for the form of its shell, which resembles, when partially expanded, a bird flying.

Shell foliaceous or not, thin and very fragile, always pearly, sub-equivalve; form sub-regular, but rather variable; summit anterior; valves oblique, the left one with a little notch, through which the byssus passes; sometimes unequally and obliquely auricled; hinge linear, toothless, or with two small rudimentary teeth; ligament more or less exterior, placed in a narrow groove, sometimes enlarged towards the summit; one very large posterior muscular impression; and one very small anterior.

Avicula macroptera. A. lotorium. A. semi-sagitta. A. heteroptera. A. falcata. A. crocea. A. Tarentina. A. Atlantica. A. squamulosa. A. papilionacea. A. costellata. A. physoides. A. virens.

_A. macroptera._ The rounded Avicula. Pl. 14, fig. 3.

Species oval, oblique, the earlike appendages very developed, especially the superior; one tooth at the hinge.

_A. Atlantica._ The Atlantic Avicula.

Obliquely curved, yellowish fawn colour, with dark reddish-brown stains; interior pearly.

5. Meleagrina. Two species.

The form of the shell is orbicular and equivalve, without the elongated transverse base on the cardinal tooth, and the sloping sides of the opening for the passage of the byssus are perceptible on both valves; these peculiarities distinguish it from the Avicula.

Shell sub-equivalve, rotundate, nearly square, externally squamose; the inferior cardinal margin straight, not caudate anteriorly; a sinus at the posterior base of the valves for the passage of the byssus; the left valve being at this place narrow and channelled; hinge linear, without teeth.

Meleagrina margaritifera. Meleagrina albina.

_M. margaritifera._ The pearl-bearing Meleagrina, sometimes called the mother-of-pearl oyster.

Species slightly oblique, somewhat square, pearly, very thick, compressed; undulated and transversely striated, with a series of lamellated longitudinal scales; exterior greenish, interior pearly. This shell is celebrated for its irridescent colours, and is valued for the beautiful and costly pearls it produces. These pearls are formed from a deposition of the substance destined to line the shell upon sand or other bodies, casually or purposely introduced within the mantle of the animal; the shell itself is the mother-of-pearl used for inlaying, or making various elegant trinkets.

FAMILY XVIII. PECTINIDES. Seven genera.

1. Pedum. The Shepherd’s Crook. One species.

The common name was given to this genus from the resemblance to a French shepherd’s crook. The shell is of a regular form; its lower valve, in which is a sinus for the byssus, is turned up at the edges, and the upper valve falls within it.

Shell inequivalve, a little eared; apices unequal, distant, rounded, little evident; hinge without teeth; ligament inserted in an oblique groove, prolonged to the summit, and carried within in a kind of spoonlike cavity.

_P. spondyloideum._ The spondylus-shaped Pedum. Pl. 15, fig. 5.

Ovate, wedge shaped, flat; superior valve with longitudinal striæ; white, granulated, and rough; slightly tinged with purple near the beak.

2. Lima. The File Shell. Six species.

No sinus or notch; the valves, thick and gaping, form a lateral opening; the ears are small, but distinct.

Shell oval, more or less oblique, almost equivalve, with small ears, regularly gaping at the anterior part of the lower edge; summits anterior and distant; hinge longitudinal, without teeth; ligament rounded, almost exterior, inserted in a cavity of each valve; central muscular impression divided into three very distinct parts.

Lima inflata. L. squamosa. L. glacialis. L. annulata. L. fragilis. L. linguatula.

_L. squamosa._ The scaly Lima. Pl. 15, fig. 3.

Answers to the above description, with valves ventricose, armed with vaulted scales.

_L. fragilis._ The fragile Lima.

Oblong ovate, very pellucid, delicately white, with longitudinal distinct striæ; lower margin denticulated, closely interlocking when the valves are closed.

3. Pecten. The Scallop. Fifty-nine species.

The shells constituting this genus are found in all seas; they are well known, and many of them are very beautiful.

The form is usually regular; their surface is adorned with elevated divergent ribs, varying in number from five to thirty, proceeding from the beaks and terminating at the margins in a scalloped outline.

Some are equivalve, others have one valve flat and the other convex; the colours of the upper valve are brighter than those of the lower.

There is considerable variation in the size and form of the ears, which in some species are equal or nearly so, but in others are unequal; some are so small as to be nearly indistinct. The ribs are variously diversified with beautiful colours and delicate checker-work; the margins are mostly crenated, and oftentimes beautifully coloured.

These shells were formerly worn by Pilgrims on their hat or coat, as a mark of having been to the holy shrine in Palestine.

Shell free, regular, thin, solid, auricled, equivalve, equilateral; summits contiguous; hinge without teeth; a ligamental membrane through all the length of the hinge, besides a short, thick ligament, almost entirely internal, which fills a triangular cavity under the summits; one sub-central muscular impression.

Pecten maximus. P. medius. P. Jacobæus. P. bifrons. P. ziczac. P. Latirentii. P. rastellum. P. turgidus. P. flagellatus. P. aspersus. P. flavidulus. P. plica. P. pleuronectes. P. obliteratus. P. Japonicus. P. Magellanicus. P. purpuratus. P. lineolaris. P. radula. P. nodosus. P. pallium. P. pes-felis. P. tigris. P. imbricatus. P. histrionicus. P. sauciatus. P. opercularis. P. asperrimus. P. senatorius. P. aurantius. P. florens. P. varius. P. sanguineus. P. sinuosus. P. ornatus. P. glaber. P. sulcatus. P. virgo. P. unicolor. P. griseus. P. distans. P. Isabella. P. lineatus. P. flabellatus. P. irradians. P. flexuosa. P. dispar. P. quadriradiatus. P. Islandicus. P. inflexus. P. pellucidus. P. Tranquebaricus. P. gibbus. P. miniaceus. P. pusio. P. hybridus. P. sulphureus. P. lividus.

_P. glaber._ The glabrous Scallop. Pl. 15, fig. 4.

Species of which the two valves are ribbed and almost equally convex, the right a little less, and having its inferior ear less broad than the left, so as to produce a kind of groove for the passage of the byssus.

_P. Jacobæus._ The scallop of St. James.

Species very inequivalve; the left valve being very flat, the right convex; ears equal.

_P. pleuronectes._ The sole Scallop.

Species equivalve, not closing; surface smooth and ribbed within; one valve perfectly white, the other of a brownish or reddish colour.

4. Plagiostoma. Ten fossil species.

Only known as fossils; probably introduced here by Lamarck to serve as a connecting link for the genera Lima, Pecten, Spondylus, and Podopsis.

Shell rather thick, regular, free, sub-equivalve, sub-auriculated; the two valves almost equally convex, both provided with a distinct summit, recurved in the middle of a level surface, with a great triangular slope in the middle; the cardinal base transverse, straight; hinge without teeth; a conical cardinal pit situated below the beak, partly internal, opening outward, and receiving the ligament.

_P. spinosa._ The thorny Plagiostoma.

Subarcuated, the umbo of one shell higher than that of the other, with longitudinal ribs and remote concentric rings.

5. Plicatula. Five species.

Separated from the Spondylus of Linnæus on account of its distinct structure. The ligament is altogether internal; it is without ears, and the prolonged beak so conspicuous in that genus. The Plicatula has the faculty of affixing itself to another body, so that many are found grouped together in clusters. The valves are strongly plaited within and without, closely interlocking with each other.

Shell solid, adhering, sub-irregular, without ears, inequivalve, pointed at the summit, rounded and plaited behind; hinge with two strong teeth in each valve, with a cavity between them, in which the ligament is internally inserted.

Plicatula ramosa. P. depressa. P. cristata. P. reniformis. P. Australis.

_P. ramosa._ The branched Plicatula. Pl. 15, fig. 2.

Oblong, trigonal, very thick; strong longitudinal plaits; exterior brown, with a yellow tinge, with reddish arrow-shaped markings; interior white.

6. Spondylus. The thorny Oyster. Twenty-one species.

The valves of this genus greatly resemble those of the common oyster, but have ears, and are covered with long recurved or straight-pointed spines.

The lower valve is much larger than the upper, and has foliaceous laminæ, by which it is attached to the other substances. They are found in all seas of hot countries, but particularly in the Indian; they adhere to rocks, coral, &c., oftentimes in large groups.

The usual colours are red, purple, white, brown, or orange, several of which are sometimes blended in the same shell.

Shell solid, adhering, sub-regular, more or less spined, sub-auriculated, inequivalve; the right or inferior valve fixed, much more excavated than the other, and having behind, at the summit, a triangular face, which enlarges and elongates with age; hinge longitudinal, provided in each valve with two strong teeth entering into corresponding cavities; ligament short, almost medial, partly exterior; one sub-dorsal, muscular impression.

Spondylus gædaropus. S. Americanus. S. arachnoides. S. candidus. S. multilamellatus. S. coccineus. S. crassisquama. S. spathuliferus. S. ducalis. S. longitudinalis. S. costatus. S. variegatus. S. longispineus. S. regius. S. avicularis. S. microlepos. S. croceus. S. aurantius. S. radians. S. zonalis. S. violacescens.

_S. gædaropus._ The thorny red Spondylus. Pl. 15, fig. 1.

Upper valve red, under one white, with longitudinal striæ or ribs; rough granulations, and somewhat tongue-shaped; rather short truncated spines.

_S. longispineus._ The long-spined Spondylus.

Thickly spined, longitudinally sulcated and ribbed; alternate spines arcuated and tongue-shaped; valves of a reddish colour; umbones orange.

7. Podopsis. Two fossil species.

Only introduced here to fill up the family and keep up the chain of connexion. It approximates the genus Gryphea.

Shell rather thick, sub-regular, symmetrical, equilateral, inequivalve, adhering by the extremity of the shorter valve; the other terminated by a summit pointed, a little recurved and medial; articulation very angular, by means of two very distant condyles.

FAMILY XIX. OSTRACEA. Six genera.

1. Gryphæa. One species.

This genus resembles the Ostrea, with which it was formerly classed, but from which it is distinguished by the peculiar character of the lower valve. It is very deep and carinated, with a summit terminating in a long spirally recurved beak, slightly turned to one side; the edge sharp and angular.

It is seldom, if ever, attached to other bodies. Shell more finely lamellated than that of the oyster, free or slightly adherent, sub-equilateral, very inequivalve; the lower valve very concave, with a summit more or less recurved like a hook; the upper valve much smaller, and formed like a lid; hinge without teeth; ligament inserted in an oblong arched cavity; one single muscular impression on each valve.

_G. angulata._ The angulated Gryphæa. Pl. 16, fig. 2.

Oblong ovate, with three long longitudinal carinated ribs below; summit of the inferior valve is subvolute. This is a rare shell.

2. Ostrea. The Oyster. Forty-eight species.

As given by Lamarck, is a natural and well-defined family. It is too well known to require description. It fixes itself to other bodies by the laminæ of the whole surface of one valve, and generally remains immoveable, exhibiting no other signs of life other than that of opening its valves to receive nutriment.

Shell irregular, inequivalve, inequilateral, exterior roughly foliaceous, interior somewhat pearly; the left or inferior valve larger, deeper, and adhesive, its summit prolonging with age in a sort of heel, the right or superior valve smaller, more or less in the form of a lid; hinge without teeth; ligament short, sub-interior, inserted in an oblong cardinal cavity, increasing with the summit; muscular impression single and sub-central.

Ostrea edulis. O. hippopus. O. borealis. O. Adriatica. O. cochlear. O. cristata. O. gallina. O. numisma. O. lingua. O. tulipa. O. Brisiliana. O. scabra. O. rostralis. O. parasitica. O. denticulata. O. spathulata. O. cornucopiæ. O. cucullata. O. doridella. O. rubella. O. limacella. O. ruscuriana. O. Virginica. O. Canadensis. O. excavata. O. mytiloides. O. sinuata. O. trapezina. O. tuberculata. O. rufa. O. margaritacea. O. gibbosa. O. Australis. O. elliptica. O. haliotidæa. O. deformis. O. fucorum. O. plicatula. O. glaucina. O. fusca. O. turbinata. O. crista-galli. O. erucella. O. folium. O. labrella. O. imbricata. O. hyotis. O. radiata.

_O. edulis._ The eatable Oyster. Pl. 16, fig. 5.

Species orbicular, and not plaited; rugged, with undulated, imbricated scales; one valve flat and the other convex; variable in size; outside greenish brown, inside pearly white, sometimes with a bluish tinge.

_O. Virginica._ The Virginian Oyster.

Species longitudinal and not plaited.

_O. imbricata._ The imbricated Oyster.

Species orbicular and plaited.

_O. crista-galli._ The Cock’s-comb Oyster.

Species strongly plaited longitudinally.

3. Vulsella. The Tweezers. Six species.

This genus has several characteristics which distinguish it from the Ostrea; they are free; the valves and the apices are nearly equal, with a projecting callosity on each valve, depressed underneath, and obliquely arched for the reception of the ligament.

Shell sub-nacreous, sub-regular, sub-equivalve, inequilateral; upper valve finely granulated, or striated longitudinally from the apex to the margin; summits anterior, distant, recurved below; hinge without teeth; ligament undivided, thick, inserted in a rounded cavity, made in a slightly projecting callosity on each valve; muscular impression sub-central, rather large, and two very small ones entirely anterior.

_V. lingulata._ The tongue-like Vulsella. Pl. 15, fig. 6.

Elongated, depressed, transversely striated; pale yellowish brown, with longitudinal darker stripes.

4. Placuna. The Chinese Window Shell. Three species.

This genus received its common name from the thin, transparent nature of the valves of the shell, particularly of the species _placenta_, which by the ingenious Chinese are often polished and used as a substitute for window-glass.

The hinge of the shells of this genus is so peculiar as to make it perfectly distinct; entirely interior, fastened by a ligament shaped like a V on one of the valves.

Shell free, sub-irregular, very thin, almost entirely transparent, flat, sub-equivalve, sub-equilateral, slightly auricled; hinge entirely internal, formed on the superior less valve by two elongated, unequal, oblique ribs converging at the summit, to the interior side of which a ligament like the letter V is inserted in two equally converging, rather deep cavities of the lower valve, which is more convex; one rather small, sub-central muscular impression.

_P. placenta._ The glassy Placuna. Pl. 16, fig. 3.

Sub-orbicular, flat, white, and transparent; finely striated longitudinally, slightly decussated.

5. Anomia. The Antique Lamp. Six species.

When Linnæus formed this genus and named it Anomia, he probably did so from its having no determinate character. Its common name was given it by the fancied resemblance of some of its species to an antique lamp. Like the oyster, they seldom leave their place; they are always affixed to marine bodies by an osseous operculum, formed by the thick extremity of the animal’s muscle. The lower valve is perforated and smaller, conforming to the shape of the substance to which it is affixed.

Shell adhering, irregular, inequivalve, inequilateral, ostraceous; inferior valve rather more flat than the superior, divided at the summit into two sloping branches, whose approaching together forms a large oval hole, through which protrudes a muscle, the extremity of which becomes ossified and adheres to extraneous bodies; one sub-central muscular impression divided into three.

Anomia ephippium. A. patellaris. A. cepa. A. electrica. A. pyriformis. A. fornicata. A. membranacea. A. squamula. A. lens.

_A. ephippium._ The Saddle Anomia. Pl. 16, fig. 1.

Shell sub-orbicular, irregularly wrinkled and waved; upper valve convex, under flat and perforated at the hinge, through which passes the ligament by which it is affixed to other bodies; inside pearly, and of various changing colours, such as green, purple, violet, and yellow.

6. Crania. The Scull. One species.

So called from the appearance caused by three holes or cavities on the surface of the lower valve.

Shell irregular, orbicular, inequivalve; the inferior valve almost flat, and marked on the interior with four muscular impressions, sometimes very deep, and of which the two sub-central are sufficiently connected to form but one; the superior valve like a Patella, more or less convex, with four very distinct muscular impressions, rather distant.

_C. personata._ The masked Crania. Pl. 16, fig. 4.