CONCHOLOGY. 41 



M. lactea. M. trigonella. 



M. abbreviata. M. deltoides. 



M. crassatella. M. alata. 



3. Genus Crassatella. 

 Animal. Unknown. 



Shell. Close, suborbicular or transverse, striated longitudi- 

 nally, denticulated, regular, equivalve, inequilateral, summits 

 well marked, and turned to the front; primary teeth somewhat 

 divergent with a hollow at the side ; no lateral teeth nor obsolete 

 ones ; ligament internal and inserted into a pit in the hinge. 

 It is easily known from the Mactra and Lutraria by the valves 

 fitting exactly. The living species of this genus only exist in the 

 seas of Australasia, while in a fossil state we find at least seven 

 species in France. Eleven species. 



Crassatella kingicola. Crassatella subradiata. 



C. donacina. C. contraria. 



C. sulcata. C. cuneata. 



C. rostrata. " C. Erycinsea. 



C. glabrata. C. cycladea. 



C. striata. 



4. Genus Erycina. 



Animal. Unknown. 



Shell. Somewhat longer than high, subtrigonal, regular equi- 

 valved, inequilateral, gaping but little or not at all ; sumits well 

 marked and a little inclined to the front ; hinge subsimilar ; two 

 unequal cardinal teeth converging to the summit ; two oblong^ 

 compressed, short, and inserted lateral teeth; ligament internal 

 and situated in a pit. Owing to the equivocal character of this 

 genus it is somewhat difficult to judge of the hinge. Inhabits the 

 Indian Ocean. One species. 



Erycina cardioides. 



5. Genus Ung^ulina, 



Jlnimal. Unknown. 



Shell. Vertical or sublongitudinal, a little irregular, not gaping, 

 5* 



