MOLLUSCA — GASTROPODS 



235 



P"iG. 102. — The marine snail, biisycon canaliculatus Say, from ihe Atlantic coast of 

 the United States, in fxjsition of feeding. A, entire adult animal. B, a portion 

 of the shell removed exposing the soft body portion within, occupying nearly the 

 entire shell. The dotted lines show the outline of the cut edges of the shell. 

 (Compare with Fig. 10.3.) e., eye; intra., introvert, partly extended ; m., mantle 

 edge; o.l.p., outer lip of shell; op., operculum; si., siphon; sp., spire of shell; 

 /., tentacles; wh., whorl or revolution. Fig. A shows a shell of six whorls. 

 (X|.) 



a tube, the siphon, open along one side ; this extends out through 

 the canal of the shell. 



The organ of respiration i.s the .single gill which lies on the wall 

 of the mantle cavity. This is a leafy expansion of the mantle, 

 consisting of a row of flattened tubes bound together at the base 



