CO'i^CRYLlA—DITHYRA. 35. 135 



The shells answering to this generic character are with much pro- 

 priety separated from the Venus, in consequence of their being fur- 

 nished with a lateral tooth in each valve, and which is generally 

 placed on the anterior or cartilage side. All the British species 

 have the internal margin very entire. 



Oyprina testa obliquS cordatd, transvershn striata, areola posticd oh- Islandica, 



soletd, dentibus tribus. 

 Shell obliquely heart- shnped, striate transversely, with the hinder 



impression obscure, and three teeth. 

 Venus Islandica. Linn. Syst. Nat. p. 1131. 



Gmelin, Syst. p. 3271. 



Turton, Linn. Syst. iv. p. 221. 



Pennant, iv. p. 205, tab. 56. 



Chemnitz, vi. p. 340, tab. 33. fig. 341, 342. 



Montagu, Test. Brit. p. 114. 



Donovan, British Shells, iii. tab. 77- 



Turton, British Fauna, p. 157. 



Linn. Trans viii. p. 83. 



Dorset Catal. p. 35, tab. 6. fig. 5. 



Dillivyn, Descript. Catal. f. 176. 



Turton, Conch. Diet. p. 238. 

 Pectunculus crassus. Da Costa, p. 183, tab. 14, fig. 5. 

 Pectunculus maximus. Lister, Conch, tab. 272, fig. 108. 

 Var. rugis crassis transversis. 



with thick transverse ridges. 

 Mus. nost. On most open coasts. 



Shell growing to four inches or more in diameter, strong, 

 thick, covered with a glossy brown or olive skin, under which it 



