226 MARINE SHELLS 



Cabinet of the Academy and Philadelphia Mu- 

 seum. 



Diners from the preceding in the form of the beak, 

 which is never arquated. 



3. C. *glauca. Shell thin, convex, glaucus, with 

 minute transverse wrinkles ; apex conic, acute, not 

 excurved, but declining and distinct from the margin 

 of the aperture ; aperture oval-orbicular ; within en- 

 tirely reddish brown ; diaphragm plain or convex, 

 less than half the length of the shell, edge widely 

 contracted in the middle. 



Length about half an inch. 

 Inhabits the coast of the United States. 

 Cabinet of the Academy and Philadelphia Mu- 

 seum. 



Very distinct from the preceding species. 



4. C. *plana. Shell depressed, flat, oblong oval, 

 transversely wrinkled, lateral margins abruptly de- 

 flected ; apex not prominent, and constituting a mere 

 terminal angle, obsolete in the old shells ; within 

 white ; diaphragm occupying half the length of the 

 shell, convex, contracted in the middle and at one 

 side. 



Length 1 and 1-10 of an inch. 

 Inhabits the coast of the United States. 

 Cabinet of the Academy and Philadelphia Mu- 

 seum. 



A remarkably distinct species, the surface of the 

 shell is flat, and sometimes slightly concave. The 



