47 



exterior, but less so than in the G. Amphidesma. — 

 Shell inequilateral suborbicular ; valves sometimes at- 

 tenuated at one end; two divergent primary teeth, 

 with a cavity at the side; lateral teeth obsolete; liga- 

 ment internal, inserted in the cavity of the hinge on 

 either side of the valves. 



Crassatella Kingicola 



donacina 



sulcata 



rostrata 



glabrata 



Crassatella subradiata 



contraria 



cuneata 



erycinaea 



cycladea 



Crassatella striata. 



ERYCINA. 



The equivocal character of these shells renders it very 

 difficult to judge of their hinge. La Marck only men- 

 tions one species, not having those before him which 

 he had described in the Ann. du Muske. Shell trans- 

 verse, su bin equilateral, equivalve, rarely gaping; two 

 unequal divergent primary teeth, with a cavity be- 

 tween ; two short, oblong, lateral, compressed, insert- 

 ed teeth ; ligament interior, fixed in the cavity between 

 the primary teeth. 



Erycina cardioides. 



