CONCIIOLOGY. 43 



Shell ovate, transverse, slightly gaping ; summits project- 

 ing ; hinge formed by two teeth on one valve, and only one 

 inserted on the other. 



P. virgata. The striped Psammobia. PL 7, fig. 1. 

 Species rather gaping, striated longitudinally, the teeth of 

 the hinge considerably effaced. 



P. Ferroensis. The Ferro Psammobia. 

 Oblong oval ; white, radiated with crimson ; finely striated 

 transversely ; valves obliquely truncated. 



3. Psammotffia. Seven species. 



Of the same form as the Psammobia, but differing in the 

 number of teeth, as the left valve of the Psammotaea has 

 only one tooth ; sometimes one valve is toothless, while the 

 other has two teeth. 



Shell transverse oval or oblong; gaping a little at the 

 sides ; one primary tooth on each valve, though sometimes 

 on only one of them ; ligament exterior, attached to callosi- 

 ties at the hinge, and without an irregular plait. 



Psammotaea violacea. Psammotaea serotina. 



P. zonalis. P. Candida. 



P. pellucida. P. Tarentina. 



P. donacina. 



P. violacea. The violet Psammotaea. PI. 7, fig. 5, 

 Transversely ovate-oblong, sub-ventricose ; transversely 

 striated ; purple radiations. 



