CONCHOLOGY. 61 
C. depressa. C. bicolor. 
C. sinuata. C. concamerata. 
C, citrina. ; C. aviculina. 
C. orbularis. C. sublevigata. 
C. lithophagella. 
C. borealis.* C. incrassata.* 
3. Genus Cypricardia. PI. VII. 
Animal. 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 and California. Five living 
species. Three fossil. 
Cypricardia angulata. Cypricardia coralliophaga. 
C. Guinaica. C. rostrata. 
C. Caiifornica.* 
4, Genus Hiatella. Pt. VII. 
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 front ; 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. In- 
habits the British seas. ‘wo species.” | 
Hiatella Arctica. Hiatella biaperta. 
5. Genus JIsocardia. Pl. VIII. 
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 papille ; 
foot small, compressed, trenchant. 
Shell. Free, regular, inflated, equivalve, very inequilateral, 
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