98 MOLLUSC A. 



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

 ma giga*, L. ; Chemn., VII, xlix, which 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 

 CHAM A, Brug., 



Or the true Chamae, the shell is irregular, inequivalve, usually 

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

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

 up. The internal cavity frequently has the same form without 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 in 

 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 sufficiently prominent to remind us of two hornsj. 

 In the 



ISOCARDIA, Lam., 



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

 summits, divided anteriorly. The animal, GLOSSUS, Poli, 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, 509; Ch. gryphcrides, Ib., 510, 513 ; 

 Ch. archinella, Id. lii, 522, 523 ; Ch. macrophylla, Ib., 514, 515 ; Ch. foliacea, 

 Ib., 531 ; Ch. citrea, Regenf., IV, 44 ; Ch. bicornis, Ib., 516 520. 



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

 Paris of M, de Lamarck. 



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

 aux Alpes, I, pi. ii, f. 1 4. 



Add Ch. moltkiana, Chemn., VII, xlviii, 484487. 



