326 THE CHICAGO ACADEMY OF SCIENCES. 



tinged with blue or purple, and reflected over the columellar 

 region and columellar lip; last whorl usually very convex, in- 

 clined to bulbous. Operculum not essentially different from 

 that of Pleurocera. 



Length, 16.50; width, 7.00: aperture length, 6.50; width, 3.50 mill. (8748.) 



18.00; " 7.50; " " 7.00; " 4.00 " (8748.) 



12.00; " 6.00; " " 6.00; " 3.00 " (8748.) 



11.00; " 6.00; " " 6.00; " 3.50 " (8748.) 



13.00; " 6.00; " " 5.50; " 3.00 " (8748.) 



15.50; " 7.00; " " 7.00; " 4.00 " (8746.) 



20.00; " 9.50; " " 9.00; " 5.00 " (12369.) 



Animal: Similar to Pleurocera in form; color bluish- white 

 on base of foot and sides; body yellowish, darker in places; 

 rostrum blackish on middle portion, yellowish at the tip; neck 

 yellowish; the rostrum is not as heavy as in the last genus. 

 There seems to be little generic difference between the animals 

 of these two genera. 



Jaw: Like that of Pleurocera, 



Radula formula:- T V + i + i + i+i + | + rV (3-1-3); the 

 teeth are similar to those of Pleurocera subulare, excepting that 

 the central tooth has four small cusps on each side of the cen- 

 tral cusp; the cusps are a little rounder in the present species 

 than in the one mentioned. 



Genitalia: Not observed. 



Distribution: New York to Great Lakes, south to Ohio 

 River drainage. 



Geological distribiition : Pleistocene; Loess. 



Habitat: Found rather plentifully on a muddy (some- 

 times sandy) bottom, in water from two to tenor more feet in 

 depth. Prefers a bottom with water weeds. 



Remarks: A very distant species, at once known by its 

 bulbous form, convex outer lip and bluish or purplish aperture 

 and columella. The spire is very broadly conic. G. milesii is 

 simply a smooth, extra bulbous form of livescens, not entitled 

 to even varietal rank. There is considerable variation in the 

 carination of the upper whorls, but all of these different forms 

 may be connected with the type by a series of specimens. The 

 individuals from Lake Michigan are always heavier and more 

 solid than those from the smaller lakes and rivers. 



The animal moves slowly, pushing its foot forward a short 

 distance and then drawing the shell after it. This is particu- 

 larly noticeable when crawling up the side of a glass jar. 



