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. (10286.) 
“4.00; « 3,00; a" “> 2,00; Creeks onan (10236.) 
Animal: Withashort, 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 
re, 125: 
Head and verge of SOMATOGYRUS INTEGER Say. (From Stimpson 
Res, on Hydorb., Fig. 13.) 
extremity bifid, one bifurcation being longer than the other; 
the inner bifurcation is the shorter and contains the canal. 
(vide Stimpson.) (Fig. 125.) 
Fic. 126. 
Radula of SOMATOGYRUS INTEGER Say. (Stimpson, Hydrobiine, Fig.11. 
Radula formula: ~yt+qpetiteaigtit dati (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 is known by its globose shell and pe- 
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