Number 145 Deckmber 21, 1923 



OCCASIONAL PAPERS OF THE MUSEUM OF 

 ZOOLOGY 



UNIVERSITY OF MICHIGAN 



Ann Arbor, Michigan Published by the University 



TWO NEW FRESHWATER SNAILS FROM 

 MICHIGAN 



By Mina L. WrNSLow 



The forms described below were found in the course of 

 field work for the Museum of Zoolog}' of the University of 

 Michigan. Both were submitted to Dr. Bryant Walker, to 

 Vvhom grateful acknowledgment is made for helpful criticism. 

 For a discussion of the subspecies of Planorbis antrosus 

 reference may be made to Dr. Walker's "Notes on Planorbis 

 JI: P. bicarinatus," in The Nautilus, Vol. XXIII. pp. i-io, 

 1909. It is interesting to find still another distinct form of 

 P. antrosus in the same general northern region from which 

 the varieties percarinotns, royalensis and portagcnsis have al- 

 ready been listed. 



Planorbis antrosus jordanensis, new subspecies 



Figs. 1-5 



Shell with four and a, half closely coiled whorls, upper sur- 

 face decidedly flattened, concave, apical whorls deeply im- 



