OYSTERS. 247 



uiriboes unequal^ somewhat divaricating and receding from 

 each other, as the area between them becomes enlarged by 

 the increase of the shell ; the valves are fibro-laminar_, and 

 sometimes foliated; the lower valve, which is uniformly 

 larger, is concave ; and the upper, or smaller valve, is gene- 

 rally flattish. Hinge destitute of teeth, and the ligament 

 is either internal or semi-internal, attached to the umbonal 

 area. The muscular impression is situated near the centre, 

 and the mark of a minute accessory cartilage has been 

 noticed beneath the hinge, analogous to the Pinnce. 



Oysters, in old times, were spoken of as occupying in the 

 scale of nature a degree the most remote from perfection : 

 they were described as being destitute of progressive mo- 

 tion, without art or industry, leading a vegetable life, in 

 perpetual imprisonment, tliough opening their shells daily 

 to admit the element needful for their preservation. But 

 the light of science and natural history, shining even into 

 the dark cells of the peaceful Oysters, has made known many 

 interesting particulars relative to their natural history. 



True it is that the mollusks of which we speak are appa- 

 rently some of the most insignificant of created beings, nay, 

 they appear little more tlian gelatinous substances ; and yet 

 these feeble creatures are conscious of their existence, and 



