SHELLS. 217 



sometimes midtlplicate, often furnished witk peculiar 

 armatures, and their intestines are variously elon- 

 gated. They have, in general, salivary glands, and 

 always a liver of considerable size, but no pancreas 

 or mesentery; several have secretions which are 

 peculiar to them. 



The food of the moUusca consists of almost all 

 sorts of substances, animal and vegetable^ — in all 

 states, living or dead, fresh or putrid; but each 

 species is in general confined to a certain kind. 



All the senses common to the higher animals are 

 found in the moUusca, though some are, doubtless, 

 wanting in the humble classes of the division. In 

 the Cephalopoda, the organs of sight and hearing 

 are distinct and well-developed; and Professor Owen 

 is of opinion that the Nautilus, an animal of this 

 class, possesses an organ of " passive smell." 



The Gasteropoda are almost invariably furnished 

 with eyes ; and, according to M. Siebold and other 

 zoologists, have ears — a pair of round capsules, 

 placed near the bases of the tentacles, and enclosing 

 one or more crystalline globules, called otoKtes. 

 Some of the Conohifera are furnished with numerous 

 eyes placed among the tentacles, examples of wliich 

 are found in the claws and scallops {Pecten) of our 

 own shores. 



