ANOMIA. MYTILUS. 27 



'^ Very well remembered," continued her father. 

 " The generic character of this very large portion 

 of bivalves is, shell bivalve, usually with unequal 

 valves : hinge without teeth, having a hollow 

 cavity or sinus, and sometimes grooved. Here is 

 a young common oyster, and, according to the 

 rule of our present system, this shell, Ostrea 

 isognomoriy is of the same genus, (Plate 5.) 

 The number of species is eighty-four, of which 

 thirteen are British. The old shells of common 

 oysters are often covered with Serpula, LepaSj 

 and Anomia, and some kinds of corallines. 



" The next genus, A7iomia, is remarkable for 

 the thin, delicate, and almost transparent ap- 

 pearance of the shells. The valves are unequal, 

 and frequently perforated near the apex ; hinge 

 toothless ; in the flat valve, two bony rays. 



" Anomia epiphippium has a large perfora- 

 tion, through which the animal passes a ligament, 

 and attaches itself to other substances. These 

 shells are often to be found on oysters. (Plate 5.) 

 Species thirty-two. 



" Mytilus. The principal characters are, shell 

 bivalve, rough, often affixed by a thick byssus, 

 or beard; hinge without teeth, with a hollow line 

 extending lengthways. (Plate 3.) 



" The common muscle, Mytilus edulis, must 

 be well known to you, and also the fine polish 

 that the shells will take when cleared of the rough 



c 2 



