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 
Common Squid, Loligo, cut transversely : a, foot or siphon ; Bb, gills; c, man- 
tle ; d, internal shell ; e, heart ; f, 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, 
