188 



being distinct and forward ; the lateral teeth remote ; the 

 ligament external. 



Venus paradoxa, Born. Galathea radiata, Ann. duMus. 

 Tom. 5. PI. xxviii. 



Concha MarinL Rarely with epedermis, or lateral 

 teeth. 



1. Cyprina. An equivalved, inequilateral, and obliquely 

 cordated bivalve ; three unequal cardinal teeth : one lateral 

 tooth on the anterior side, sometimes obsolete. 



2. Cytherea. An equivalved, inequilateral, suborbicular, 

 trigonal or transverse shell ; four cardinal teeth on the right 

 valve ; three diverging, approximated at their base, and one, 

 entirely separate, under the lunule ; three diverging cor- 

 responding teeth in the other valve ; with a separate pit for 

 the separate tooth of the other valve. No lateral teeth. 

 Recent and fossil. PL viii. fig. 13. 



3. Venus. An equivalved, inequilateral, transverse, or 

 suborbicular shell; three cardinal approximated teeth on 

 each valve, the lateral ones diverging from the summit ; the 

 ligament external. Recent and fossil. PL viii. fig. 7. 



CardiacecB. Teeth irregular either in form or situation. 



1. Venericardia. An equivalved, inequilateral, subor- 

 bicular bivalve, most commonly with longitudinal ribs ; the 

 hinge, two cardinal teeth, nearly in the same direction. 

 Recent and fossil. PL viii. fig. 2. 



2. Cardita. A free, inequilateral, equivalved bivalve ; 

 the hinge with two unequal teeth, one short and straight 

 under the beaks, the other oblique and marginal, extended 

 beneath the corselet. Recent and fossil. PL vii. fig. 27. 



3. Cardium. A subcordiform equivalve, protuberant at 

 the base, the valves plicated or dentated on their inner 

 margin. The hinge with four teeth in each valve ; two 

 oblique approximating cardinal teeth, those of each valve 



