XI 



PHYLUM MOLLUSC A 



289 



with a protrusible proboscis or introvert, sometimes of con- 

 siderable length. On the dorsal surface of the head are a 

 pair of tentacles, which vary a good deal in shape, but are 



FIG. 164. Cypraea moneta (Cowrie). Showing the mantle, provided with marginal 

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

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



usually cylindrical or club-shaped. In most cases the eyes 

 are situated on tubercules at the bases of the tentacles, or 

 elevated towards the middle ; but in the Snails and Slugs 



lr 



FIG. 165. Doris (Archidoris) tuberculata. a. anus ; br. branchiae ; 1/1. penis ; 

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



(Pulmonata) they are elevated on the extremities of a 

 second, longer, pair of tentacles (Fig. 159, oc. tent.) placed 

 behind the first. 

 Man. Zool. 



