CYPRINA. 303 



paring the beaks to a ram's horns. Knorr, in his 

 f DeliciaB Naturae selectse/ says it is called in France 

 " coeur de boeuf," and in Holland " zots-kappen " or 

 fool's-cap. 



It is the Bucardia communis of Schumacher and Iso- 

 cardia Hibernica of Reeve. 



Genus II. CYPBTNA * Lamarck. PL VI. f. 2. 



Body suborbicular and fleshy : mantle rather thick, slightly 

 retractile ; edge finely serrated : tubes extremely short, but 

 separate ; orifices cirrous : foot large and extensile. 



Shell heart-shaped, convex, concentrically striated: epi- 

 dermis thick and fibrous : beaks incurved : hi aide and corselet 

 wanting : ligament almost wholly external : teeth, in each valve 

 three cardinals, the outer one laminar, besides a single lateral 

 on the posterior side. 



We now approach the boundaries of the Venerid<e. 

 Clark was of opinion that Isocardia might very well 

 merge in the present genus, because the animals of both 

 were similar ; but the points of resemblance are common 

 to the family, and there are other characters in which 

 these genera may be distinguished from each other. 

 The difference will appear from a comparison of the 

 generic descriptions given above. Lamarck supposed 

 that Cyprina was allied to Cyrena, and partook of a 

 fluviatile nature, by reason of its substantial epidermis 

 and strong lateral teeth; and he stated that Cyprina 

 Islandica inhabits the mouths of rivers. This is not the 

 case : it is exclusively marine. The only recent species 

 known to us is widely scattered over the seas of the 

 northern hemisphere on both sides of the Atlantic : its 

 fossil remains have been found in every part of the vast 

 territories comprised within the 3Gth and 80th degrees of 



* From Kt>7rpjs\ one of the names of Venus. 



