316 THE CHICAGO ACADEMY OF SCIENCES. 



pointed, the whorls convex; sutures well marked, sometimes 

 bordered by a faint white line; color varying from light yel- 

 lowish horn to pale brown ; sculpture as in gyri?ia, the lines being 

 very deep and the wrinkled ridges very convex; protoconch 

 consisting of one and one-half smooth, rounded, wine-colored 

 whorls; aperture oval, rather wide, produced at the anterior 

 end, about two-thirds the length of the entire shell; peristome 

 thin, thickened within the aperture by a heavy white or 

 yellowish-white callus, which shows through the shell very 

 plainly; it is never bordered by a color stripe; the callus of 

 two or three former peristomes may always be seen on the 

 body whorl and sometimes one or two on the spire; columella 

 broad, flat, white, a callus spreading over the parietal wall. 



Length, 12.00; width, 8.00; aperture length, 7.50; width, 3.00 mill. (12352.) 



10.50; " 7.50; " " 7.50; " 3.50 " (12352.) 



" 10.00; " 6.00; " " 5.50; " 3.00 " (12352.) 



Animal: Not differing essentially from gyrina. 



Jaw: Similar to that of gyrina. 



Radula: Similar in form to that of gyrina, but differing 

 in having six large, nearly equal cusps, instead of five, in the 

 general absence of small cusps between the larger ones, and 

 in the reflection being wider than in gyrina or heterostropha. 

 The radula of this species is remarkably uniform in the form 

 of the teeth and in the number of the cusps. The central 

 tooth and secondary teeth appeared to be the same as in the 

 species previously described. 



Distribution: Great Lakes and St. Lawrence River; In- 

 diana, Illinois, Tennessee, Michigan, and Wisconsin. 



Geological distribution : Pleistocene. 



Habitat: At stations similar to gyrina. 



Remarks: This species has been generally confounded 

 with heterostropha, but will at once be separated from that spe- 

 cies by the spiral lines; the general form is also different from 

 that of any shell found in this area, and the white callus on the 

 lip is peculiar. It is a common shell at Hickory Creek, Lock- 

 port and Joliet, and has been found more sparingly at Calumet 

 Grove, Maywood, and Edgewater. It is more common than 

 sayii, but less so than gyrina. The specimens from Hickory 

 Creek are quite typical, resembling closely Haldeman's figures 

 (PI. 4, Figs. 7, 8) in his monograph of fresh-water Mollusca. 

 This species is a biannuan. 



