402 The Molluscan Family Plauorbidae 



PLATE 83 



Shells of Planorbidae 



1-3. Helisoma anceps sayi F. C. Baker. Tomahawk Lake, Oneida Co., Wisconsin. 



Type locality. U.I., Z25736. 

 4-6. Helisoma anceps sayi F. C. Baker. West Lake Okoboji, Iowa. Shimek coll. Vary- 

 ing toward anceps. U.S.N.M., 475945. 

 7-9. Helisoma anceps unicarinatum (Haldeman). Plum Point, Delaware River, above 



Riverton, New Jersey. TJ.L, Z25938. 

 10-12. Helisoma anceps unicarinatum (Hald.). Cherokee River, Little River Station, 



Alabama. U.I., Z41055. 

 13-15. Helisoma anceps unicarinatum (Hald.). Blackstonc River, above Courtland, 



West Virginia. Figure 13 resembles Haldeman's angisiomum. LT.S.N.M., 109888. 

 16-18. Helisoma anceps politum F. C. Baker. Honeywell Creek, Carleton Co., 



Ontario, Canada. F. R. Latchford coll. Holotype, fig. 16; paratypes, figs. 17, 



18. U.S.N.M., 367426. 

 19-22. Helisoma anceps bartschi F. C. Baker. Brook at Great Falls, Virginia. Holotype, 



fig. 19; paratypes, figs. 20-22. U.S.N .M., 227858. 

 23-25. Helisoma anceps (Menke). Variety? Mouth of Yaqui River, Northwest Mexico. 



LT.S.N.M., 53677. 

 26. Helisoma anceps (Menke). Variety? Potomac River. U.S.N.M., 364718. 

 27-29. Helisoma anceps aroostookcnse (Pilsbiy). Woodland, Aroostook Co., Maine. 



Type locality. U.I., Z21015. 



Figures are enlarged approximately two diameters 



