HETEROCARDIA. 387 



very small, close to the cardinal tooth ; cartilage-pit pro- 

 duced into the cavity of the shell ; ligament marginal, near 

 the cartilage. 



Ex. C. turgida, Deshayes, pi. 102, fig. 5, 5, a. 



The shells comprised in this group inhabit the mud of 

 shallow bays ; the surface of the valves is covered with an 

 olivaceous or green epidermis, and the sides are closed. 



Species of Ceecella. 



Chinensis, Desk. tenuis, Desk. 



ctmvexa, Desk. transversalis, Desk. 



Cumingiana, Desk. turgida, Desk. 



lata, Desk. Zebuensis, Desk. 



oblonga, Desk. Zelaudica, Desh. 



Genus HETEROCARDIA, Deshayes. 



Shell transversely ovate, sub- trigonal, transversely stri- 

 ated, gaping posteriorly; beaks minute. Hinge narrow, 

 cardinal lamina narrow, canaliculated. Sinus of pallial 

 impression very deep, extending as far as the anterior mus- 

 cular scar. 



Ex. H. gibbosula, Deshayes, pi. 102, fig. 6, 0, a. 



The genus Heterocardia comprises but few species, 

 which are from the Philippine Islands. 



Species of Heterocardia. 



Cumingii, Desh. gibbosula, Desh. 



fabagella, Desh. 



