90 
MOLLUSCA. 
Inoceramus, Sowerb. 
Is remarkable for the elevation and inequality of the valves, the 
summit of which curves in a hook towards the hinge, and which has 
a lamellated texture * * * § . 
Castillus, Brong. 
Independently of the depressions for the ligament, the Castilli are 
marked hy a conical sulcus, sunk in a lip, which is bent at a right an- 
gle to form one of the margins of the shell. The valves are about 
equal, and of a fibrous texture. They appear to have had a byssusf. 
PuLViNiTEs, Defr. 
A regularly triangular shell, in Avhich the few depressions diverge 
from the summit on the inside. The impression is found in chalk :j;. 
In the second subdivision of the Ostracea, as well as in almost all 
the bivalves which follow, besides the single transverse muscular mass 
of the preceding genera, there is a fasciculus which is placed before 
the mouth, and extends from one valve to the other. It is apparently 
in this subdivision that we must place the 
Etheria, Lam. 
Large inequivalve shells, as irregular as those of the Ostrcfe, and more 
so ; no teeth to the hinge ; the ligament partly external and partly 
internal. They differ from the Ostreae in having two muscular im- 
pressions. The animal is not seen to produce a byssus §. 
They have lately been discovered in the Upper Nile 1 |. 
Avicula, Brug. 
An equivalve shell with a rectilinear hinge, frequently extended into 
wings by its extremities, furnished with a narrow and elongated liga- 
ment, and sometimes with small notches near the mouth of the ani- 
mal; in the anterior side, a little beneath the angle of the side of the 
mouth, is a notch for the byssus. The anterior transverse muscle is 
excessively small. 
The species with less salient ears form the Pintadin^e, Lam., or 
MargaritjE, Leach. 
The most celebrated, Mytilus margariti ferus, L., Chemn., VIII , 
Ixxx, 717? 721, has nearly a semicircular shell, greenish without. 
* Inoceramus concentricus, Parkins., Cuv., Oss. Foss., II, pi. vi, f. 11 ; — Inocer. 
sulcaius, Id., Ib., f. 12. 
't' Calillus Cuvieri, Brong., Cuv., Oss. Foss., II, pi. iv, f. 10. 
X Puh'initss Adansonii, Defr., Blainv., Malac., Ixii, bis, 3. 
§ Elheria ellipHca, Lam., Ann. du Mus. X, pi. xxix, and xxxi ; — Efh. irujonula, 
lb., pi. XXX ; — Elh. seminularis, lb., pi. xxxii, f. 1, 2; — Eth. transversa, Ib., f, 
3, 4. 
II Elh. CuiUaudi, Voy. dc Caillaud a Meroe, II, pi. Ixi, f. 2, 3. 
