CLASSES AND SUB-KINGDOMS. 



181 



CHAPTER XXIY. 



CLASSES AND SUB-KINGDOMS. 



THE following figures illustrate the classes and sub-king- 

 doms which have been dealt with in this book, with their 

 technical names : 



SUB-KINGDOM MOLLUSCA (Clams, Snails, /Squids, etc.). 



Class Gasteropoda (snails, periwinkles, limpets, etc.). 

 Animals whose bodies are generally inclosed in a mantle or 

 sac, which usually secretes a shell composed of one piece, and 

 this often assuming a spiral shape. The body rests upon a 

 broad, creeping disk called the foot, and this part represents 

 the ventral portion or belly of the animal. The name Gas- 

 teropoda is derived from two Greek words, gaster, the belly, 

 and pous, foot. The following figures represent a few ani- 

 mals of this class : 



