58 



MOLLUSC A. 



species which remain among the western Pacific islands 

 and Indian Ocean (East Indies) (N. pomp.) are tlie 

 last remnants of a host of extinct types which peopled 

 the sea in geologic ages. 



This shell is frequently seen in the shops, but should 

 be split open on the lapidary's wheel, in order to show 

 the structure of the internal chambers, and the long 

 connecting-pipe which unites them. 



The various forms of these shells and of the animal 

 are described in all general works on the Mollusca ; and 

 it is merely necessary to notice that the shell is turned 

 or built in a direction which reverses that of the inter- 

 nal pen or shell of the Squids (Fig. 41) and Cuttle 

 Fishes; and, like the Argonauta (Fig. 43), has the 

 funnel and the ventral part of the body turned to 

 the outside. This is directly the reverse, also, of the 

 position of the animal in the shell among the Gas- 

 teropoda. 



SQUIDS AND OCTOPUS. 



These remarkable forms can only be mentioned, but 

 they are too important and interesting to be skipped 

 entirely. 



The body consists of a fleshy bag, hollow in front, 

 and surmounted by a head, furnished with large eyes, 

 and a circle of tentacles or arms surrounding the 

 mouth, which is situated in the forward end (Fig. 41). 

 Inside of the mantle, on the dorsal side, is a long, 

 horny shell, or pen, as it is called. 



The mouth has powerful jaws of horn, formed like a 

 parrot's beak, and also teeth inside, situated upon the 

 tongue. The arms are covered with sucking discs, so 

 that they can firmly fasten themselves to their prey, and 



