458 CARDIID/E. 



Genus HEMICARDTA, Klein. 



Shell cordate, keeled, very short, hinder side shorter or 

 impressed ; lunule simple ; valves closed, and smooth or 

 nearly smooth behind. Hinge with the cardinal teeth dis- 

 tinct, more or less distorted. 



Syn. Cor, Meusch. Corculum, Hebenstr. Cardissa, 

 Miihlf. Isocardia, Oken, not Lam. or Klein. Hemicar- 

 dium, Cuv. 



Ex. H. cardissa, Linnaus, pi. 112, fig. 3, 3, a. 



The members of this group are pretty numerous, and are 

 met with on the shores of most temperate and tropical 

 countries. The shells of the typical examples are very 

 peculiar, from their compressed, heart-shaped form. 



Species of Hemicardia. 



cardissa, Linn. lineata, Gmel. 



Dionsea, Brod. mid Sow. monstrosa, Chem. 



humana, Chem. unimaculata, Sow 



Sub-gen. fragum, Bolten (Hemicardium, Swains., not Cuv.) 



Shell half-heart-shaped, the anterior side abruptly truncate 

 and very short, the hinder side often longer than the anterior ; 

 beaks carinated ; ribs smooth, or nodulose. 



biangulata, Brod. and Sow. imbricata, Born. 



carditseformis, Reeve. lseva, Swains. 



donaciforruis, Spengl. media, Linn. 



fasciata, Mont. munda, Beeve. 



fragum, Linn. nivalis, Beeve. 



hemicardium. Linn. nodosa, Mont. 



