NAUTILUS-&4/ZO/?. 137 



within its boat, draws in water, and immediately 

 disappears. Though capable of floating on the 

 surface of the sea, it is often found reversed, and 

 like a snail bearing its house upon its back. The 

 name is derived from the Greek word >atmXo$ 

 (nautilos) a sailor. 



The animals inhabiting the shells of this and 

 the following genus vary considerably from the 

 other mollusca ; they are called Cephalopodes,* 

 (footed at the head,) because their heads are 

 surrounded by arms or tentacula. Their bodies 

 are fleshy like the other mollusca, and the pos- 

 terior portion is contained in the mantle of the 

 animal. The mouth is vertical and armed with 

 two corneous mandibles resembling the beak of a 

 parrot. They live in the sea, are carnivorous, 

 and feed on crabs and other marine animals. The 

 position of their arms enables them to seize their 

 prey, and bring it to their mouth. The Cephal- 

 opodes which form a multilocular shell, instead 

 of being enclosed within it, envelop it so as only 

 to leave a small portion visible : a tendinous 

 thread which issues from the extremity of the 

 body appears to attach the latter to the shell, it 

 probably has some connection with the siphun- 

 culus. 



As in the genus Teredo we observed how ex- 

 tensive a work of destruction is carried on by a 

 little worm, here we have to notice the reverse of 



* Cephalopodes. Having feet on the head, from the Greek 

 (kephale) ahead, and7ro5 (podes) feet. 



