3G4 



CUAMID^.- 



-5I0LLUSCA.- 



-Cardiid^. 



ciliated fringe of tlie upper orifice of the mantle moved 

 slowly, as if in search of auimalcula. Having remained 

 in this position about ten minutes, water was ejected 

 with considerable force from the lower orifice, which 

 till now had remained motionless. The expulsion of 

 the water appeared to be effected by a sudden contrac- 

 tion of the muscles, because tliis was never done without 

 tiie valves nearly closing at the same time. After a few 

 seconds the valves gradually returned to their open 

 position, and remained quiescent as before, till the water 

 was again ejected with a jerk. The Heart Cockle 

 burrows in sand, forcing its way by means of its sharp 

 pointed, triangular foot, leaving only the siphonal 

 openings exposed. Only five species are known, one of 

 whicli is an inliabitaut of the British seas and the 

 Mediterranean, and the others are natives of China 

 ajid the Philippine islands. 



Family— CHAMID^. 



Tlie Chanias have an inequivalve, iiTegular shell, 

 ailhering to other substances, as rocks, shells, and corals, 

 by the outer surface of one of the valves, usually the 

 left one. The beaks are recurved, unequal, and the 

 hinge is composed of two teeth in one valve, and a 

 single large tooth in the other. The valves externally 

 are generally foliaceous, and vary very much in form 

 and colour. Their shape is usually determined by the 

 body to which they are fixed. The species are almost 

 all from tropical seas, and they especially affect coral 

 reefs. The genus is represented in Plate 10, fig. 4, by 

 Chama luzanis. 



Family— ANATINIDiE. 



The Lantern-shells have usually a thin, brittle, oblong, 

 often inequivalve shell, gaping at the hinder extremity, 

 with a nacreous interior, and generally a granular or 

 6[>inulose exterior. The hinge is obscurely toothed, the 

 cardinal teeth being rudimentary ; the ligament is ex- 

 ternal, thin, and the cartilage is internal, placed in a 

 pit in each valve, and furnished with a peculiar shelly 

 hinge-piece or ossicle, which is placed before it, or 

 sometimes so as to cover the whole of its surface. 

 The family contains several genera. 



Genus Anatina or Laternula. — This genus, the 

 Lantern- shell, has a ventricose, thin and translucent 

 shell, of an oblong form, gaping and attenuated at 

 the hinder extremity. The beaks, which are directed 

 backwards, are fissured or slit externally, and are suf)- 

 ported internally by an oblique plate. The cartilage 

 pit in this genus is placed on a projecting spoon-shaped 

 process, which is furnished in front with a transverse, 

 linear ossicle. The external surface of the valves is 

 hispid, or roughened with calcareous points. 



Genus Thracia. — This genus has the cartilage 

 placed on a thick, not prominent, callous process on 

 the hinge margin, and has a cresceutic ossicle. Some 

 of the species are found in crevices of rocks, and in the 

 burrows of Saxicava, and have in consequence been 

 sometimes mistaken for boring shells. 



Genus Cua.mostrea. — This genus has a shell 

 varying considerably in form and appearance from 



the typical species of Anatinidce, but has the internal 

 cartilage and ossicle peculiar to the family. The shell 

 is inequivalve, like that of the Chama, solid, and attached 

 by the anterior side of the deep and strongly-keeled 

 right valve. The left valve is flat, and has a conical 

 tooth in front of the cartilage, which is furnished with 

 an oblong, curved ossicle, not unlike the human clavicle. 

 As yet only one species is known ; it is a native of the 

 seas of Australia. 



Family- MUTELID^ (= Iridmdce). 



Notwithstanding the fluviatile habitat, and Unio-Wke 

 general appearance of the shells of this family, they 

 come into this sub-order, as we find the animal having 

 the mantle lobes united and produced into two separate 

 siphons. The shells are solid, oblong, equivalve, pearly 

 within, and externally covered with a hard polished 

 epidermis. The hinge is large, linear, and either 

 toothed or toothless. The species of this family are all 

 natives of fresh water, and are found either in Africa or 

 South America. 



Genus Mutela {■^Irklinn). — This genus has an in- 

 equilateral, transverse shell, with the hinge margin 

 smooth, without teeth, and attenuated towards the 

 beaks, which are small, recurved, and nearly straight. 

 The species of Mutela are natives of the rivers of 

 Africa. One is found in the Nile [M. exotica), and 

 the valves are used by the natives of Egypt as spoons 

 in measuring oil, butter, and dilVerent kinds of pro- 

 visions. 



Genus Pleiodon. — This genus (represented in 

 Plate 10, fig. 5, by Pleiodon ovatum), has an ovate, 

 strong, and convex shell, with the hinge margin slightly 

 arched, which, becoming broader at its extremities, is 

 furnished witli a series of large, irregular teeth, or 

 tubercular crenations. The outer surface of the valves 

 is covered with a dark, olive epidermis, and the interior 

 is brilliantly lighted up with an iridescent silvery nacre 

 generally tinged with pink. The two or three known 

 species are all from Africa. 



The other genera are Leila, Castai.ia, and Hyuia, 

 the species of which are all natives of the fresh waters 

 of South America. 



Family— CARDHD^. 



The Cockles have a regular, equivalve, usually in- 

 flated, and more or less heart-shaped shell, generally 

 ornamented with radiating ribs and furrows. The 

 margins interiorly are crenulated ; the ligament is ex- 

 ternal, short, and prominent, and the hinge is composed 

 of two oblique cardinal teeth, and two elongate, lamellar 

 laterals in each valve. The pallial line is simple, or 

 slightly sinuated behind. The animals have the foot 

 angularly bent behind, enabling them to make leaps, 

 prodigious in proportion to their size — the Cardium 

 nori-eijicimi being said to be able to effect such junjps 

 as to spring out of the vessel in which it is held in 

 captivity. The species of this family are very numer- 

 ous, upwards of two hundred having been described ; 

 and are distributed over the whole world, from north 

 to south, from east to west, and range from the sea- 



