CEPHALOUS MOLLUSCA. 
Ae take leave of our little decapitated friends of Headless Molluscaor 
■A-cephahe, and direct our attention to those molluscs to which Nature 
has been more generous, and furnished with a head. This head, how- 
ever, is still carried humbly ; it is not yet os sublime declit; it is drawn 
along an inch or so from the ground, and in no respect resembles the 
proud and magnificent organ which crowns and adorns the body of the 
greater and more perfectly organized animals. 
The organization of the Cephalous Mollusca present three principal 
types, which has led to their being divided into three classes, after 
their more salient characteristics of form and locomotive apparatus ; 
namely, Gasteropoda, Pteropodm, and Cephalopoda). 
In the class Gasteropoda (from yaaryp, belly, 7ro0y, gen. ttoSos, foot) 
the locomotive apparatus consists of a flattened muscular disk, placed 
Wilder the belly of the animal, aided by which it creeps. The Snail 
{Helix aspersa), the Slug (Limax rufus), and the Porcelains (Cijprea 
%n's), are type3 of this class. 
In the Pteropoda, from irrepov, wing, and ttovs, foot, the locomotive 
a Pparatus assumes the form of wings, or membranous swimming- 
hns, placed on each side of the neck. The Hyalea and Clio are types 
°t this class. 
In the Cephalopoda, from ae^aXi), head, and 7 row, foot, the locomo- 
tive apparatus consists of arms, or tentacles, which surround the mouth 
l n numbers more or less considerable. The Cuttle-fish (Sepia), and 
*he Poulpes (Odopodm) are types of this last class. 
