YENUS. 399 



Abroad it has its chief centre in the Lnsitanian Province, 

 and is abundant in the INIediterranean. It was an inhabit- 

 ant of our seas as long ago as the epoch of the coralHne 

 crag but retired southwards during the prevalence of glacial 

 conditions, and afterwards returned. 



SPURIOUS. 

 C. ciRciNATA, Born. 



Voms circinata. Born, Mus. Cees. Vindob. p. Gl, pi. 4, f. 8. — Chkmn. Conch. 



Cab. vol. vi. p. 312, pi. 30, f. 311.— Dillw. Recent Shells, 



vol. i. p. 169. 

 Venus Guineensis, Gmelin, Sj^st. Nat. p. 3270. — Mont. Test. Brit. Suppl. pp. 



48, 168 Dorset Catalog, p. 35.— Turt. Conch. Diction. 



p. 237. 

 Cytlierea Guineensis, Lam. Anim. s. Vert. (ed. Desh.) vol. vi. p. 311. — Turt. 

 Dithyra. Brit. p. 161. — Flem. Brit. Anim. p. 445. — 

 Brit. Marine Conch, p. 84.— Hanl. Recent Shells, p. 100. 

 Encyclop. Method. Vers. pi. 2G5, f. 1, 



Inhabits the S. Atlantic Ocean; was introduced by Montagu, as 

 taken in the Frith of Forth by Mr. Laslcey. 



VENUS, LiNN^us. 



Shell often thick, equivalve, closed, more or less subor- 

 bicular or transversely ovate, generally ornamented by con- 

 centric ribs or striaj, in some species decussated by longi- 

 tudinal furrows, often brightly coloured. Margin crenated. 

 Beaks prominent. Hinge composed in each valve of three 

 diverging cardinal teeth. Ligament strong, external, 

 lodged in a well-defined area. Lunule well-marked. Mus- 

 cular impressions rounded, strongly marked. Pallial sinus 

 lanceolate, wide. 



Animal ovate or suborbicular, thick ; its mantle open 

 throughout, and fringed or furbelowed at the margins. 

 Siphons separate, and diverging, or partially, or even eu- 



