118 



GASTKOPODA. 



tentacles ; foot rounded in front, its sides moving 

 alternately. 



P. pullus. Fig. 174 ; f. 



175 



Trochus (Linn.). Top. Shell pyramidal, nearly 

 flat at the base ; aperture oblique, somewhat four- 

 sided ; pearly ; operculum horny, many-whorled. 

 Animal with two minute head-lobes, large neck- 

 lappets, side-lobes, and filaments. 



T. alabastrum. 

 cinerarius. 

 conulus. 

 exiguus. 

 granulatus. 

 helicinus. 

 crassus. 

 magus. 



T. millegranus. 

 Montagui. 

 pusillus. 

 striatus. 

 tumidus. 

 umbilicatus. 

 undulatus. 

 zizipHnus. Fig. 175 ; n.s. 



Adeorbis (Wood). Shell minute, depressed, 

 few-whorled, deeply umbilicated ; operculum shelly, 

 many-whorled. 



A. sub-carinata. Fig. 176 ; f . 



