402 CHAMIDJ5. 



receive the internal ligament. Anterior muscular impres- 

 sion rounded, superficial ; posterior on a thin, horizontal 

 lamina, projecting into the interior. 



Syn. Hemicyclonosta, Desk. 



Ex. C. semisulcata, Lamarck, pi. 112, fig. 6, 6, a. 



There are only three species of this genus as yet described, 

 which are inhabitants of the China Sea and the Philippines. 



Species of Cardilia. 



inermis, Desk. semisulcata, Lam. 



Martini, Desk. 



Fam. CRAMIDM. 



Labial palps small, curled, obliquely truncate. Mantle 

 closed, the margins united by a curtain fringed -with tenta- 

 cular filaments ; siphonal orifices small, wide apart, the 

 branchial slightly prominent, with the orifice fimbriated, the 

 anal with a simple valve ; gills two on each side, unequal, 

 plicate, the outer pair very short and narrow, united to each 

 other behind and to the mantle. Foot cylindrical, bent. 



Shell inequivalve, irregular, adherent; beaks unequal, 

 recurved or sub-spiral. Hinge furnished with two teeth 

 in one valve, and a single large tooth in the other; liga- 

 ment external. Muscular impressions large, reticulated; 

 pallial line simple. 



Living attached to stones and rocks. 



Genus CHAMA, Linnaeus. 



Shell irregular, inequivalve, adherent ; beaks recurved, 

 unequal. Hinge composed of a single thick, oblique, sub- 



