58 



VENUS. 



A. Subcordate. (Plate VII. fig. 2.) 



B. Orbicular, (fig. 3.) 



C. Oval, a little angular on the anterior mar- 

 gin, (fig. 4.) 



Shell having the lips incumbent on the anterior 

 margin. Hinge with three teeth, all approxi- 

 mate, the lateral ones diverging fiom the apex. 

 The area and areola are well defined. In this ge- 

 nus the beaks are uniformly, or with very few ex- 

 ceptions, turned towards the posterior slope, that 

 is,J'rom the ligament. By this character they are 

 distinguished from many of the Tcllinre, which 

 otherwise resemble them, as well as from some 

 species of different genera which have no remote 

 lateral teeth. 



The first section A includes all the shells which 

 are nearly cordiform, as well those which are fur- 

 nished with spines on the circumference of the 

 area, as those which are merely wrinkled, striated, 

 or smooth. They are very different in external 



