CONCHOLOGY. 51 



on the largest side ; in some species the lateral teeth are 



crenulated, in others they are entire. 



Cyrena trigonella. Cyrena fuscata. 



C. orientalis. C. fluminea. 



C. cor. C violacea. 



C. depressa. C Bengalensis. 



C. Caroliniensis. C. Ceylanico. 



C. fluminea. The river Cyrena. PI. 6, fig. 7. 



Species sub-trigonal or elongated oval ; summits decorti- 

 cated, more anterior ; three cardinal teeth, of which the two 

 posterior are forked ; exterior greenish brown, interior va- 

 riegated with white and violet ; sulcated transversely. 



3. Galathea. One species. 

 This beautiful shell is found in fresh waters, and is dis- 

 tinguished from the Cyrena by the divergent form of the 

 primary tooth. 



G. radiata. The radiated Galathea. PI. 6, fig. 8. 



Shell equivalve, sub-trigonal, covered with a greenish epi- 

 dermis, beneath which the surface is of a milky white, highly 

 polished, with several violet or pale chestnut rays diverging 

 from the apex to the margin ; primary teeth furrowed, two 

 on the right valve joined at the base, three on the other valve 

 placed triangularly, the intermediate one being advanced, 

 separate, thick, and callous ; the muscular impressions are 

 lateral, and appear double on each side. 



C. Marine. Four genera. 



4. Cyprina. Two species. 



This shell is generally large, resembling the Venus, from 



which it may be distinguished by having on the front side 



one impressed lateral tooth, which is sometimes obsolete ; 



the nymphae or callosities of the hinge large, arched, and 



terminated near the apices by a cavity, sometimes very deep. 



De Blainville says that this genus is intermediary to the 



