Cephalopoda. 147 



They have been classed according to the head into 

 Acephala (headless, clams), Cephalophora (head-bearing, 

 snails), and Cephalopoda (head-footed, squids). 



The classification here adopted is based on the foot and 

 presents three chief classes : 



1. Pelecypoda (hatchet-footed); example, the clam. 



2. Gastropoda (stomach-footed); example, the snail. 



3. Cephalopoda (head-footed); example, the squid. 



