OF CONCHOLOGY. 7 



placed on the right side, within the 

 shield ; feelers four, situate above the 

 mouth, and an eye at the tip of each 

 of the largest ones. 



This genus is what is generally 

 termed the slug, or snail. 



2nd. DORIS. 



Body, creeping, oblong, and flat 

 beneath ; mouth placed below, on the 

 fore-part; vent behind, on the back, 

 and surrounded by a fringe ; feelers, 

 two and four, seated on the upper 

 part of the body in front, and retrac- 

 tile within their probu receptacles. 



3d. SPIO. 



Body projecting from a tube, joint- 

 ed and furnished with dorsal fibres ; 

 peduncles, or feet, rough with bristles 

 and placed towards the back ; feelers 

 two, long, simple ; eyes two, oblong. 



