CONCHOLOGY. 



51 



united ; mouth small ; labial appendages quite small ; branchiae 

 wide, short, free, or not united either with one another, or with 

 those of the opposite side. 



Shell. Solid, equivalve, regular, inequilateral ; summits equal, 

 reflexed, and slightly projecting ; four primary teeth on one valve, 

 of which three are divergent, and approximating at the base, and 

 one remote — this circumstance easily distinguishing it from the 

 Venus. On the other valve are three primary divergent teeth 

 with a distant cavity parallel with the edge. Inhabits the British 

 and Mediterranean seas. Eighty living species. Nine fossil. 



Cytherea petechialis. 



C. morphina. 



C. Castanea. 



C casta. 



C. lusoria. 



C. graphica. 



C. impudica. 



C. purpurata. 



C. zonaria. 



C. corbicula. 



C. meretrix. 



C. tripla. 



C. erycina. 



C. impar. 



C Guiniensis,' 



C pectoralis. 



C. Arabica. 



C. florid a. 



C immaculata. 



C. Chione. 



C. hepatica. 



C. citrina. 



C. lactea. 



C. lata. 



C. lincta. 



C. trigonella. 



C. prostrata. 



Cytherea tigrina. 

 C. pulicaris. 

 C. numulina. 

 C abbreviata. 

 C. pectinata. 

 C. flexuosa. 

 (J. ranella. 

 C. lunularis. 

 C. divaricata. 

 C. lunaris. 

 C. placunella. 

 C. cygnus. 

 C. juvenilis. 

 C. gigantea. 

 C. Venetiana. 

 C. lilacina. 

 C. rufa. 

 C. erycinella. 

 C. Dione. 

 C. planatella. 

 C. trimaculata. 

 C. nitidula. 

 C. pellucida. 

 C. maculata. 

 C. lucinalis. 

 C. albina. 

 C. exoleta. 



