254 ZOOLOGY. 



This is divided into three families, * having radiated 

 equal or unequal ears ; ** surface of the shells rough and 

 PLATED on the outside ; *** hinge with a perpendicular 



GROOVED LINE. 



Oysters are esteemed as a delicate and nutritious food; 

 and the shells of some of the kinds are converted to many 

 useful purposes ; they all inhabit the ocean, and are gene- 

 rally found in great numbersj either among sand .or adhering 

 to rocks and stones. They are familiarly divided into 

 Oysters and Scallops, our figure represents one of the latter 

 kinds. 



15. Anomia. 5Ae^/ inequivalve ; one of the rfl/rc5 flattish, 

 the other gibbous, one or both valves are often perjo' 

 rated near the hinge. Plate 4, fig. 1 6. 



This genus is confined to the ocean, the s pecies being 

 often found affixed by a ligament that passes through the 

 perforation, to various kinds of fuci, and other substances. 



16. Mytilus. Muscle. Inhabitant allied to an Ascidea. 



Shell mostly adhering to some extraneous- ubstance, by 

 its silky beard ; hinge without teeth, having in most 

 kinds a longitudinal hollow line, often crenulate. 

 Plate 4, fig. 17. 



Muscles are found in the sea, rivers, lakes, and ponds, 

 generally affixed to other substances ; some kinds perforate 

 rocks, where they ever after reside ; such as frequent fresh 



