ANOMIA-ANTIQUE LAMP. 185 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



This genus contains a variety of shells mate- 

 rially differing in their appearance : the perfora- 

 tion in one of the valves for the emission of a 

 ligament, by which the animal adheres to marine 

 substances, is, perhaps the most general, though 

 not an invariable characteristic. 



The Anomise are now arranged in two principal 

 groups, which are very clearly distinguished from 

 each other. The shells of one division retain the 

 name of Anomia, and very much resemble a small 

 oyster in their appearance ; like it they are fixed 

 and stationary, living and perishing on the spot 

 where the egg was first deposited. They are at- 

 tached by means of a bony appendage, having a 

 dilated base ; this is in fact only a prolongation 

 of the adductor muscle of the animal ossified at 

 its outer extremity. When the mollusk contracts 

 the muscle, the dilated portion is drawn over the 

 perforation of the flattened valve and covers it, 

 acting as an operculum. So firmly are the shells 

 fixed by this organ, that they cannot be removed 

 from their retreat, without destructive violence, 

 the ligament and operculum being left on the rock 

 to which they were cemented. The form of the 

 Anomia, like that of all stationary shells, is very 

 irregular, being usually modified by the sub- 

 stances to which it adheres. The prevailing co- 

 lour of this genus is a dingy yellow, or dusky 



