300 MANUAL OF THE MOLLUSCA. 



pallial line simple ; hinge-teeth 1:2, striated, in front of cartilage pit ; lateral 

 teeth 1, 1 ; adductor impressions deep, rounded ; pedal small, distinct. 



Animal with mantle-lobes united only by the branchial septum ; inhalent 

 margins cirrated; foot moderate, compressed, triangular grooved; gills 

 smooth, unequal, outer semi-lunar, inner widest in front ; palpi triangular. 



Distr. 30 sp. Australia, N. Zealand, Philippines, India, W. Africa, 

 Canaries, Brazil. 



Fossil, 50 sp. Neocomian . Patagonia, U. S. Europe. 



ISOCARDIA, Lam. Heart-cockle. 



Etym. Isos, like, cardia, the heart. Type, I. cor. PI. XX. fig. 3. 



Syn. Glossus, Poli ; Bucardium, Muhlfeldt ; Pecchiolia, Meneghini. 



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

 nal; hinge-teeth 2:2; laterals 1 1 in each valve, the anterior sometimes 

 obsolete. 



Animal with the mantle open in front ; foot triangular, pointed, com- 

 pressed ; siphonal orifices close together, fringed ; palpi long and narrow ; 

 gills very large, nearly equal. 



Fig. 217. Isocardia cor. 



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

 the siphonal openings exposed. (Bulwer.} 



Distr. 5 sp. Brit. Medit. China, Japan. 



Fossil, 70 sp. Trias . U. S. Europe, S. India. 



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

 diomorpha and Iso-arca ; many of those in the Oolites to Ceromya. Casts 

 of true Isocardia have only two transverse dental folds between the beaks, 

 and no longitudinal furrows. 



CYPRICARDIA, Lam. 

 Ex. C. obesa, PI. XX. fig. 4. Syn. Trapezium, Humph. Libitina, Sch. 



