CYPRINA. 303 



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

 'Deliciae Naturae selectse/ says it is called in France 

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

 foolVcap. 



It is the Bucardia communis of Schumacher and Iso- 

 cardia Hibernica of Reeve. 



Genus II. CYPRI'NA *, 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 : lunule 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 Venerida. 

 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 36th and 80th degrees of 



* From KvTrpts, one of the names of Venus. 



