88 



CONCHOLOGY. 



5. Genus Calyptrea. PI. X. 

 Animal. The same as preceding genus. 



Shell. This genus derives its common name, *' the Cup and 

 Saucer Limpit," by having in the interior cavity a cup shaped 

 appendage, which is sometimes vertical, and sometimes like a 

 horse shoe, with a muscular impression of variable form, vertex 

 ending in a small volution ; smooth, margin entire, very glossy 

 within and provided with a laminar plate. Inhabits the Chinese 

 seas. Eight species. 



Calyptrea porcellana. Calyptrea equestris. 



C. fornicata. C. tecum-sinense. 



C. peziza. C. scutellata. 



C. angulata. C. poculum. 



6. Genus Crepidula. 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 ; branchisB 

 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. Seven species. 



Crepidula extinctorum. Crepidula uguiformis. 



C. aculeata. C. dilata. 



C. Iffivigata. C. Peruviana. 



C. gigas. 



7. Genus Ancylus. PI. X. 



Aniinal. 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. Three species. 



