THE NATURAL HISTORY SURVEY. 



345 



the mouth on the lower side; tentacles short, pointed, taper- 

 ing, carried resting by the side or base of the rostrum, never 

 elevated as in the pulmonates; eyes situated on the outer side 

 of swellings at the base of the tentacles; verge very large, sit- 



FIG. 127. 

 Animal of POMATIOPSIS LAPIDARIA Say. (Binney, Fig. 187.) 



uated in the middle of the back, some distance behind the 

 head, coiled one and one-half times, end pointed, outer margin 

 smooth, inner margin wrinkled (Fig. 127). Operculum thin, 

 horny, subspiral, not differing materially from Amnicola limosa 

 Say. 



Radula formula: i+i+i+T+u+i+i+HS * 3)l central 

 or rhachidian tooth as broad as high, tride'ntate, denticles on 

 base of attachment two on each side, directed inward; inter- 



FIG. 128. 



Radula of POMATIOPSIS LAPIDARIA Say. (From Nature, after Stimp- 

 son.) C, central tooth; 1, intermediate tooth; 2, 3, lateral teeth. 



mediate tooth longer than wide, four-denticulate; lateral teeth 

 narrower than intermediate, five-denticulate the denticulations 

 subequal (Fig. 128). 



Distribution: New York to Iowa, Michigan to Missouri and 

 Georgia. 



Geological distribution: Pleistocene; Loess. 



Habitat: Living, in fresh water or on land (amphibious), 

 frequenting, when in water, the vicinity of fresh- water plants; 



