COKCSirEEA. 467 



Synonyms, Glossus, Poll ; Bucardium, MuMfeldt ; Peccliiolia, 

 Meneghini. 



Shell cordate, ventricose ; umbones distant, sub-spiral ; 

 ligament external ; binge-teetk 2.2 ; laterals 1 — 1 in each valve, 

 the anterior sometimes obsolete. 



Animal with the mantle open in front; foot triangular, 

 pointed, compressed; siphonal orifices close together, fringed; 

 palpi long and narrow ; gills very large, nearly equal. 



Fig. 260 Isocardia cor. 



The heart-cockle burrows in sand, by means of its foot (/), 

 leaving only the siphonal openings exposed. (Bulwer.) 



Distribution, 5 species. Britain, Mediterranean, China, Japan. 



Fossil, 90 species. Trias — . United States, Europe, South 

 India. 



The Isocardia-shaped fossils of the old rocks belong to the 

 genera Gardiomorpha and Iso-arca ; many of those in the 

 Oolites to Ceromya. Casts of true Isocardice. have only two 

 transverse dental folds between the beaks, and no longitudinal 

 furrows. 



CyI^ricabdia, Lamarck. 



Example, C. obesa, PI. XX., Fig. 4. C. rostrata, Fig. 261. 



Synonyms, Trapezium, Himiph. Libitina, Sch. 



Shell oblong, with an oblique posterior ridge ; umbones 

 anterior depressed; ligament external, in deep and narrow 

 grooves ; cardinal teeth 2.2, laterals 1 — 1 in each valve, some- 

 times obscure ; muscular impressions oval (of two elements) ; 

 pallial line simple. 



