CONCHOLOGY. 57 



0. calyculata. C. rufescens. 



C. nodulosa. C. subaspera. 



C. trepezia. C. intermedia. 



C. depressa. C. bicolor, 



C. sinuata. C, concamerata. 



C. citrina. C. aviculina. 



Corbularis. C. sublevigata. 

 C. lithophagella. 



3. Genus Cypricardia. 

 jiniinal. As above. 



Shell. Obliquely elongated, equivalve, inequilateral ; valves 

 striated, not ribbed ; distinguished from the Cardita by having 

 three teeth beneath the apices, and a callous lengthened tooth or 

 ridge. Inhabits the coast of Guinea. Four living species. 

 Three fossil. 



Cypricardia angulata. Cypricardia coralliophaga. 



C. Guinaica. C. rostrata. 



4. Genus Hiatella. 



Animal. Unknown. 



Shell. Thin, elongated, subrhomboidal, equivalve, very ine- 

 quilateral, gaping at its inferior edge, and at its posterior extre- 

 mity ; summit very anterior, and much flexed to the f/ont ; hinge 

 formed of a single tooth upon one valve corresponding to an 

 emargination in the opposite valve, or of a small tooth with a 

 cardinal pit upon each valve ; ligament exterior and dorsal. Inha- 

 bits the British seas. Two species. 



Hiatella Arctica. Hiatella biaperta, 



5. Genus Isocardia. 



Animal. Body very thick : edges of the mantle finely papilla- 

 ceous, separated inferiorly, and united behind by a transverse 

 band, pierced with two orifices surrounded with radiating papillae ; 

 foot small, compressed, trenchant. 



Shell. Free, regular, inflated, equivalve, very inequilateral, 

 with diverging summits, strongly flexed anteriorly and outwardly, 



