60 BIVALVES. ANOMIA. 



losities, which serve as a base for the animal; but some 

 have only one in each valve. 



The interior of the shell is often silvery, and the mar- 

 gin is frequently crenated, notched, or toothed, but in 

 many it is perfectly entire. 



The prevailing color in this genus is that of a dirty 

 yellow, or dusky white; however, some are bright yel- 

 low, as the A. electrica. The A. cepa (the onion peel), 

 and the A. sella (the saddle oyster), have a fine coppery 

 or bronze-like appearance; and the A. capensis and A. 

 sanguinolenta exhibit a beautiful pink or red coloring. 

 The A. flexuosa, and other similar species, have a dingy 

 or olive black color, and a few are found of a shining 

 jet black. 



Some of the Anoniiae are almost smooth; others, on the 

 contrary, are ribbed and striated, as the A. spinosa and 

 A. muricata, which are covered with scales and hollow 

 spines of considerable length; and others decline on the 

 fore-part, and have a groove or channel running down 

 the middle of the shell. 



The Anomice are generally thin and delicate shells, 

 and usually semitransparent. The A. placenta (the cake) 

 but commonly called the Chinese window oyster, when 

 in a young state, becomes so transparent by the process 

 of polishing, that it is frequently made use of by the in- 

 genious Chinese as a substitute for glass. 



The European, Indian, American, and African oceans, 

 supply many species of the Anomia, as also do the Medi- 

 terranean and Northern seas. 



No less than fifteen or sixteen species are met with in 

 a fossil state; which are chiefly found in England,^ Ger- 

 many, and Switzerland. 



