94 ; CONCHOLOGY. 
C. fornicata. C. tecum-sinense. 
C. peziza. C. scutellata. 
C. angulata. , C. poculum. 
C. striata.* 
6. Genus Crepidula. Pl. X. 
Animal. Head anteriorly forked, having two conical tentacula, 
with the eyes placed at their exterior base; mouth simple, desti- 
tute of jaws, and situated in the bifurcation of the head; branchie 
with tufts and projecting from the branchial cavity ; the mantle 
never bordering the shell; foot minute, orifice lateral. 
Shell. Ovate, or oblong; the back almost always convex, 
concave beneath ; the spire very much inclined towards the mar- 
gin ; the aperture partly closed by a horizontal lamina. Inhabits - 
the American seas. Thirteen species. 
Crepidula extinctorum. Crepidula unguiformis. 
C. aculeata. C. dilata. 
C. levigata. C. Peruviana. 
asa 
C. gigas. 
C. fornicata.* C. plana.* 
C. depressa.* C. intorta.* 
C. glauca.* : C. convexa.* 
7. Genus Ancylus. Pl. X. 
Animal. Body creeping, enveloped in the shell; two com- 
pressed subtruncated tentacular, with eyes situated at their inter- 
nal base ; foot short, elliptical ; somewhat narrower than the body. 
Shell. Thin, obliquely conical ; aperture oval, with a pointed 
apex, which very much inclines backwards ; margins simple. This 
is a fresh water shell, found in the lakes of Europe and rivers of 
America. Five species. 
Ancylus lacustris. Ancy lus fluviatilis. 
A. spinarose. : 
A. rivularis. A, filosus. ; 
