434 



THE CHICAGO ACADEMY OF SCIE.NCES. 



slightly twisted, as is also the axis of the inner whorls of adult speci- 

 mens. Young specimens resemble pctersi but have a less number of 

 whorls, besides differing in rotundity, the whorls of petersi being en- 

 tirely without angularity. The umbilicus varies from a rather wide 

 chink to a round hole, the aperture in specimens with this kind of an 

 umbilicus being entire and almost separated from the body whorl. The 



Fig. 51. 



whorls vary greatly in angularity and in their general form. When 

 perfect, randolphi is one of the finest of our American Lymnaeas, at- 

 taining a length of an inch and a half | 41 mill. i. 



The writer cannot agree with Dr. Dall in referring randolphi to 

 Radix. Its affinities, judging by the shell alone, are entirely with the 

 cmarginata group of the genus Galba. The specimens from near Coll- 



