98 
MOLLUSCA. 
Such is the celebrated and enormous sliell of India, the Cha- 
ma gigas, 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 
Chama, Brug., 
Or the true Chamte, 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 without any 
external indication of the fact. The animal,— Psilopus, Poll,— 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. 
Die ERAS, Lam., 
Between Diceras and the Chamae 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, 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 ordinaiy 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. yryphoules, Ib., 510, 513 
Ch. archinella, Id. lii, 522, 523 Cft. macrophylla, Ih., 514, 515 CA. foliacea, 
Ib. 531 ; — Ch. citrea, Regenf., IV, 44 ; — Ch. bicornis, Ib., 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. moltkiuna, Chemn., VII, xlviii, 4S4 — 487. 
