278 THE CHICAGO ACADEMY OF SCIENCES. 



gitudinally banded; surface shining, covered with numerous 

 closely crowded growth lines, sometimes showing very fine 

 impressed spiral lines which reticulate the surface; the growth 

 lines are also wavy and elevated, in some specimens forming 

 elevated ridges of considerable size; apex smooth, brownish 

 or blackish; whorls six to seven, elongate-rounded, last whorl 

 dilated (compressed in some forms), reflexed; spire very long 

 and pointed, occupying about two-thirds of the entire length 

 -of the shell; sutures impressed; aperture lunate or elongate- 

 ovate, narrowed at the upper part, very oblique in some speci- 

 mens; peristome whitish, thin, sharp, thickened by a heavy 

 callus on the inside, the callus chocolate or purplish in color; 

 lower part of peristome dilated; columella oblique, with a 

 heavy plait across its center, running up into the whorl and 

 extending to the apex; the columella callus is heavy, wide and 

 spreading, and, with the columella, is reflected so as to com- 

 pletely cover the umbilicus; umbilical region indented. 



Length, 36.50; width, 11.00; aperture length, 14.00; width, 7.00 mill. (8111.) 

 34.00; " 10.00; " " 13.00; " 6.00 " (8111.) 



" 30.50; " 9.50; " " 12.50; " 5.50 " (8109.) 



40.00; " 13.00; " " 15.00; " 8.50 " (8109.) 



38.00; " 10.00; " " 13.50; " 6.50 " (8110.) 



31.00; " 9.50; " " 12.00; " 7.00 " (8110.) 



Animal: Bluish-black or black; foot short and wide, 12.50 

 mill, long, 6.50 mill, wide; other characters as \n palustris. The 

 head is carried but little in advance of the edge of the shell. 



Jaw: As usual. 



Radula formula: ft + f+ V+1+ V+t+i* (40-1-40); 

 central tooth as usual; lateral teeth with asubquadrate base of 

 attachment; reflection large, a little longer than wide; bicus- 

 pid, the inner cusp very large and sub-bifid, the second part 

 represented only by a swelling on the inner side of the cusp; 

 the outer cusp is short and narrow, and pointed; intermediate 

 laterals and marginals tricuspid, the center cusp long, the outer 

 cusps short; as the marginals are approached the reflection 

 becomes narrow and the outer cusp is placed nearer the top of 

 the tooth; marginal teeth long and narrow, of the usual type 

 (Fig. 91). 



Genitalia: Not observed. 



Distribution: Northern United States and Canada, from 

 the Atlantic to the Pacific. 



Geological distribution: Pleistocene; Loess. 



