74 CONCHIFERA. 



P. niveus. P. tigrinus. 



opercularis. Fig. 117 ; J- n. s. varius, 

 pusio. 



118 119 



Anomia (Linn.). Perforate Oyster. Shell round- 

 ish, thin, transparent, pearly ; left valve convex ; 

 right flat, perforated or notched close to the hinge, 

 the muscle passing through this hole to be in- 

 serted into a plate, which is cemented to foreign 

 bodies. 



A. aculeata. 



ephippium. Fig. 118 ; J n. s. 

 patelliformis. 



Ostrea (Linn.). Oyster. Shell very unequal- 

 valved, the left being convex, the right flat ; the 

 left valve is usually cemented to rocks, or to other 

 shells ; surface irregularly plaited, with free edges ; 

 hinge toothless. 



0. edulis. Fig. 119; J.*. 



