CONCHOLOGY. 59 



dermis ; the surface beneath is white, with several violet streaks 

 radiating from the summit to the margin ; two furrowed cardinal 

 teeth upon one valve, three upon the other, the middle one being 

 largest and callous; muscular impressions double and lateral. 

 Inhabits the rivers of Ceylon. One species. 

 Galathea radiata. 



FAMILY X. 



Cahdiacea. Five Genera. 

 1. Genus Cardium. PI. VII. 

 minimal. Body somewhat inflated ; mantle edged with tenta- 

 cular cirri in all its inferior part ; tubes united, of moderate size, 

 and provide with cirri at the extremity; mouth transverse, very 

 wide, with moderate labial appendages ; foot very large, cylindri- 

 cal, somewhat inclined anteriorly ; branchiae thick, rather small, 

 especially the external laminae : the internal united in all their 

 extent. 



Shell. Inflated, equivalve, sub-cordiform (when viewed ante- 

 riorly, usually costated from the apex to the circumference) ; 

 summits very evident, but shghtly flexed to the front ; hinge com- 

 plex, similar, formed of two oblique, conical cardinal teeth, and of 

 two distant lateral teeth, upon each valve ; ligament dorsal, poste- 

 rior and very short. Inhabits the European and American seas. 

 Fifty-seven living species. Fourteen fossil. 



Cardium indicum. Cardium costatum. 



C. Asiaticum. C. ringens. 



C. fimbriatum. C. tennicostatum. 



C. aculeatura. C. psudolima. 



C. tuberculatum. C. erinaceum. 



C. apertum. C. Basilianum. 



C. bullatum. C. papyraceum. 



C. echinatum. C. ciUare. 



C. biradiatum. C. levigatum. 



C. pectinatum. C. eolicum. 



C. isocardium. C. elongatum. 



C. angulatum. C. rugosum. 



C. serratum. C. unedo. 



