CONCHIFERA OR BIVALVES. 91 



pressed, and the species forming it united to 

 the genus Cardita in the following family. 



Family 9. — Cardiidce.* 



The Cardiidce, or Cockle family, are the next 

 in order ; there are four genera. The cardinal 

 teeth are irregular both in form and situation, 

 and there are generally one or two lateral teeth. 

 The shells are usually globular, and are almost 

 all marked with raised ribs ; they often present 

 also the form of a heart, when they are seen 

 on the side upon which the ligament is placed. 



50. Cardium. — Shell heart-shaped, equi- 

 valve, nearly equilateral, 

 having generally radiated 

 ribs, and the borders of the 

 valves toothed or plaited, 

 two cardinal and two la- 

 teral teeth in each valve, 

 ligament exterior, bosses 

 prominent. Animal, foot large. — 48 species 

 recent, and 30 fossil. 



Some of the species are very beautiful, and 



* Les Cardiacees, Lamarck. 



