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MANUAL OF ZOOLOGY 



The foot varies in the extent of its development in the 

 different families of the class. It usually presents an 

 elongated, flat, ventral surface on which the animal creeps 



Fig. 176. — Cypraea moneta (Cowrie). Showing the mantle, provided with marginal 

 tentacles, partly enveloping the shell. Br, branchia; M, M, mantle; F, foot; 

 T, tentacles at the edge of the mantle. (From Cooke, after Quoy and Gaimard.) 



by wave-like contractions of the muscular tissue. In the 

 typical Gastropods the foot is usually distinguishable into 

 three parts, a middle part or mesopodium which is the most 



Fig. 177. —Doris (Archidoris) tuberculata. a, anus; br, branchia; m, penis; 

 rh, rh, tentacles. (From the Cambridge Natural History.) 



important, with a smaller anterior propodium and posterior 

 mctapodium. The whole foot becomes reduced in a few 

 Gastropods that remain fixed. The metapodium very fre- 



