74 WEST COAST SHELLS 



Cardium elatutn, Sb}^, the Giant Cockle, is the 

 largest species of the genus, some specimens being 

 fully six inches high. Its range is about the same 

 as that of the last species. It is yellowish externally, 

 but white inside, and the smooth ribs are very 

 slightly elevated. 



Cardium suhstriatum^ Conr., the 

 Egg-shell Cockle, is another south- 

 erner, very much smaller than the 

 last, for Figure 48 represents an 

 unusually large specimen. Obscure 

 ribs are generally visible, and the 

 shell is mottled, especially inside. 

 Fig. 48. X 3 with reddish-brown splashes, like 



a sparrow's egg. 

 Cardiuvi quad rig enarium^ Conr., the Forty-ribbed 

 Cockle, is another southern species, and it grows in 

 deep water to a remarkable size. In spite of its 

 name the ribs are usually rather more than forty in 

 number. While the shell is young the ribs are com- 

 paratively smooth, but when it is older the newer 

 parts are set with yellow teeth, or short horns, giv- 

 ing the shell a very peculiar appearance. The strong 

 crenulations on the edges of the valves are also yel- 

 low, especially in adult specimens. 



Serripes gronlandicus^ Gmel., the Greenland 

 Heart-shell, is an arctic species coming down to 

 Cape Cod and Puget Sound, like Cardium ciliatum. 

 Its hinge-teeth are small and almost obsolete, and 

 the surface is smooth or only slightly radiately 

 striate. 



