CLASSIFICATION AND CREATION. 



59 



on__the_side of the head, and are_very large in 

 proportion to the size of the animal. A skin 



correspo nding 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-Fisho, Spuds, and Nautili, and has a 



Common Squid, Loligo, cut transversely : a, foot or siphon ; b, frills ; c, man- 

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



vast number of fossil representatives. Many of 

 these animals are destitute of any sheilj and, 



Common Squid, Loligo, in a swimming attitude. 



with a -ingle exception, w hen they have a shell, 

 it is not coi led from right to left or from left 

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

 from behind forwards, as in the Nautilu s. Ti- 

 lls are usually divided into a number of 

 chambers, — the animal, as it grows, building a 

 wall behind it at regular intervals, and always 

 upying the external chamber, retaining, 



