CONCHOLOGY. 37 



C. rostrata. C. erycinaea. 



C. glabrata. C. cycladea. 



C. striata. 



C. sulcata. The furrowed Crassatella. PI. 6, fig 4. 



Shell ordinarily thick, striated transversely, denticulated, 

 sub-triangular, equivalve, inequilateral, summits well marked 

 and evidently turned forward ; hinge very large, subsimilar, 

 formed by two diverging cardinal teeth, separated by a large 

 pit ; ligament almost entirely interior, and inserted in the pit. 



C. Kingicola. The King's Island Crassatella. 



Ovate, orbicular ; yellowish white, with obsolete rays ; 

 very minutely striated transversely ; the umbones somewhat 

 plicated. 



4. Erycina. One species. 



The only living species of this genus is found on the sand 

 in New-Holland, but there are many fossils in France. It 

 is so equivocal in character that it is difficult to judge of 

 their hinge. 



E. cardioides. The cardium-shaped Erycina. PI. 6, 

 fig. 5. 



Shell rather longer than high, sub-triangular, regular, equi- 

 valve, inequilateral, rarely gaping ; the summits well marked 

 and a little anteriorly inclined ; hinge subsimilar ; two un- 

 equal cardinal teeth, converging at the summit, and leaving 

 a pit between them ; two lateral teeth, not distant, lamel- 

 lous, inserted ; ligament interior, fixed in the cavity between 

 the primary teeth. 



5. Ungulina. Two species. 



This genus is very remarkable for having the pit or cavity 

 divided into two parts, the one at the end of the other ; the 

 ligament is partially seen from the outside. 



Ungulina oblonga. Ungulina transversa. 



