94 



CONCHOLOGY. 



C. fornicata. 

 C. peziza. 

 C. angulata. 



C. tecum-sinense. 

 C. scutellata. 

 C. poculum. 



C. striata. 



6. Genus Crepidiila. PI. 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; branchiae 

 with tufts and projecting from the branchial cavity ; theTDantle 

 never bordering the shell ; foot minute, orifice lateral. 



Shell. Ovate, or oblong ; the back almost afways 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. laevigata. C. Peruviana. 



C. fornicata.* 

 C. depressa.* 

 C. glauca.* 



C. plana.* 

 C. intorta.* 

 C. convexa.* 



7. Genus Ancylus. PI. X. 

 Jlnimal. 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. Ancylus fluviatiUs. 



A. spinarosse. 



A. rivularis. 



A. filosus. 



