418 The Molluscan Family Planorbidae 



PLATE 91 



Shells of Planorbidae 



1-4. Helisoma winslowi (F. C. Baker). Little Arbor Vitae Lake, Vilas Co., Wisconsin. 



Paratypes. Figure 4, immature. X 31/1-. U.L, Z18637, Z19398. 

 5. Helisoma pilsbryi (F. C. Baker). Chetek Lake, Barron Co., Wisconsin. B. 

 6-8. Helisoma pilsbryi preblei F. C. Baker. Knee Lake, Manitoba. Figure 6, holotype; 



7-8, paratypes. U.S.N.M., 180279. 

 9-12. Helisoma subcrenatum (Carpenter). Idaho. Shimek Coll., U.S.N.M., 504310. 



13. Helisoma subcrenatum (Cpr.). Third Vermilion Lake, below warm sulphur cave, 



Alberta. Pathologic specimen. U.S.N.M., 272105. 



14. Helisoma subcrenatum (Cpr.). Lake La Hoche, British Columbia. U.S.N.M., 43346. 



15. Helisoma subcrenatum (Cpr.). Locomotive Springs, Kelton, Utah. U.S.N.M., 308926. 

 16.18,19. Helisoma subcrenatum variety? Utah Lake, 2 miles south of Lehi, Utah. 



B1894. 

 17. Helisoma subcrenatum variety? Same locality as above. Variation toward subcre- 

 natum. B1894. 



All figures, excepting 4, are enlarged about V/j diameters 



