CONCHTFERA. 



467 



Synonyms, Glossiis, Poll ; Bucardium, Muhlfeldt ; Pecehiol ^a, 

 Menegliiui. 



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

 ligament external; hinge-teeth 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 Jsocardia 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 Cardiomorpha 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. 



Cypricardia, Lamarck. 



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



Synonyms, Trapezium, Humph. Libitina, Sch. 



Shell oblong, with an oblique posterior ridge ; umboneg 

 anterior dej^ressed; 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. 



