342 



THE CHICAGO ACADEMY OF SCIENCES. 



len, all rapidly enlarging in size; peristome sharp, simple, 

 rather thick, the edge placed obliquely to the axis of the shell; 

 columellar lip thickened by a somewhat heavy callus which 

 covers the umbilicus, leaving only a faint indication of perfor- 

 ation; base of shell rounded. 



Length, 3.50; width, 3.00; aperture length, 2.50; width, 1.50 mill. (10236.) 

 " 4.00; " 3.00; " " 2.50; " 1.75 " (10236.) 



Animal: With a short, rounded foot; tentacles of medium 

 size, rather thick at the base and tapering to a point; eyes 

 placed on swellings at the outer, upper side of the tentacles; 

 rostrum short, blunt, very large; verge very large, swollen, the 



FIG. 125. 



Head and verge of SOMATOGYRUS INTEGER Say. 

 Res. on Hydorb., Fig. 13.) 



(From Stimpson 



extremity bifid, one bifurcation being longer than the other; 

 the inner bifurcation is the shorter and contains the canal, 

 (vide Stimpson.) (Fig. 125.) 



FIG. 126. 

 Radula of SOMATOGYRUS INTEGER Say. (Stimpson, Hydrobiinse, Fig. 11. 



Radula formula: ^+^+^+^+1+^+^(3-1-3); see 

 generic description (Fig. 126). 



Distribution: Ohio Valley; Ohio west to Iowa, Michigan 

 south to Kentucky. 



Geological distribution: Pleistocene. 



Habitat: Found on muddy on clayey bottom in water 

 from five or six inches to five or six feet in depth. 



Remarks: S. integer \s known by its globose shell and pe- 



