454 CARDIlDiE. 



Genus CARDIUM, Linneeus. 



Shell globose, thick or thin, gihbose, nearly equilateral, 

 more or less gaping posteriorly, the margins often serrated ; 

 valves sometimes with elevated, keeled, membranaceous, 

 radiating ribs. 



Ex. C. edule, Linnaeus, pi. Ill, fig. 6. Shell, C. cos- 

 tatum, Linnaeus, fig. 6, a, 6, b. 



The dentition of the hinge in this genus is composed 

 of two primary teeth in each valve, placed so as to form 

 a cross when the valves are closed. The shell is more or 

 less heart-shaped, the radiating ribs which proceed from 

 the prominent beaks are usually scaly or spiny, and the 

 hind slope is sculptured differently from the rest of the 

 surface. The species are generally distributed. 



Species of Cardium. 

 costatum, Linn. hians, Brocchi. 



Sub-gen. pectunculus, Adanson (Bucardium Gray). 



Shell globose, solid, costated; binder gape narrow, aud 

 strongly toothed on the binder edge. 



Belcheri, Brod. and Sow. pseudofossile, Reeve. 



coronatura, Spengl. ringens, Chem. 



incarnatum, Reeve. Sinense, Sow. 



Iudicum, Lam. vertebratum, Jonas. 

 lima, Spengl. 



