98 



Such is the celebrated and enormous sliell of India, the Cha- 



ma a 



cjtga^. 



L. : Chemn., VII, xlix, wliich is decorated with broad 



ribs relieved by projecting semi-circular scales. Specimens 

 have been taken that weighed upwards of three hundred pounds. 

 The tendinous byssus which attaches them to the rocks, is so 

 thick and stout that the axe is required to sever it. The flesh, 

 though tough, is edible. In 



Hippopus, Lam. 



The shell is closed and flattened before as if truncated*. In the 



Chama, Briuj., 



Or the true Chamj^, the shell is irregular, inequivalve, usually 

 lamellar and rough, adhering to rocks, corals, &c., like that of an 

 Oyster. Its summits are frequently very salient, unequal, and curled 

 up The internal cavity frequently has the same form Avithout any 

 external indication of the fact. The animal,— Psilopus, Poli,— has a 

 small foot bent almost like that of man. Its tubes, if it have any, 

 are short and disjointed, and the aperture in the mantle, which 

 transmits the foot, is not much larger. Some species are found m 

 the Mediterranean. 



There are also several that are fossilf. 



DicERAS, Lam., 



Between Diceras and the Chamse there is no essential difference ; 

 the cardinal tooth of the former is very thick and the spiral lines of 

 the valves are siifficiently prominent to remind us of two horns^;. 

 In the 



IsocARDiA, Lam., 



We observe a free, regular, and convex shell, with spirally curled 

 summits, divided anteriorly. The animal,— Glossus, Poll,— only 

 differs from that of an ordinary Chama in having a larger and more 

 oval foot, and because the anterior opening of its mantle begins to 

 resume its ordinary proportions. 



A large, smooth, red species, the Chama cor. L. ; Chemn., VII, 

 xlviii, 483, inhabits the Mediterranean §. 



* Chama Lazarus, Chemn.. VII, li, 507, 609 ■,—Ch. gnjphoMes, lb., 510, 513 ;— 

 Ch archinella. Id. lii, 522, 523 ;— CT. macrophyUa, lb., 514, 515;— C/i. foliacm, 

 ib' 531 ;—Ch. citrea, Regenf., IV, 44 ;—Ch. bicornis, lb., 516—520. 



t See the Conchiol. Foss. Subap. of Brocchi, and the Coq. Foss. des Env. de 

 Paris of M. de Lamarck. 



+ Fossil shells from the Jurassic strata. Die arietina, Lam de Saussure, Voy. 

 aux Alpes, I, pi. ii, f. 1 — 4- 



§ Add Ch. mnltkiana, Chemn., VII, xlviii, 484—487. 



