CLASSIFICATION AND CREATION. 59 



on the side of the head, and are very large in 

 proportion to the size of the animal. A skin 

 corresponding to the mantle envelops the body, 

 and the gills are on either side of it ; the 

 stomach with its winding canal, the liver, and 

 heart occupy the centre of the body, as in the 

 other two classes. This class includes all the 

 Cuttle-Fishes, Squids, and Nautili, and has a 



a 



Common Squid, Loligo, cut transversely : a, foot or siphon ; ft, gills ; c, man- 

 tle ; d, internal shell ; e, heart ; /, main cavity, with intestines. 



vast number of fossil representatives. Many of 

 these animals are destitute of any shell ; and, 



Common Squid, Loligo, in a swimming attitude.- 



with a single exception, when they have a shell, 

 it is not coiled from right to left or from left 

 to right, as in the spiral of the Gasteropoda, but 

 from behind forwards, as in the Nautilus. These 

 shells are usually divided into a number of 

 chambers, the animal, as it grows, building a 

 wall behind it at regular intervals, and always 

 occupying the external chamber, retaining, 



