68 BIVALVES. — ANOMIA. 



The hinge of the Anomia admits of considerable vari- 

 ation ; but its most leading character is that of being fur- 

 nished with a linear prominent cicatrix, and a lateral tooth 

 placed within. On the margin of the flattest valve in 

 many species are placed two bony rays, or linear callosities, 

 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 margin 

 is frequently crenated, notched, or toothed, but in m.any it 

 is perfectly entire. 



The prevailing colour in this genus is that of a dirty yel- 

 low, or dusky white; however, some are bright yellow, 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. sanguinea 

 exhibit a beautiful pink or red colouring. The A. psittacea, 

 and other similar species, have a dingy or olive black co- 

 lour, and a few are found of a shining jet black. 



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

 contrary, are ribbed and striated, as the A. muricata, which 

 is 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 Anomiae are generally thin and dehcate 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 po- 

 lishing, that it is frequently made use of by the ingenious 

 Chinese as a substitute for glass. 



The European, Indian, American, and African oceans 

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

 diterranean and Northern seas. 



