220 The Molluscan Family Planorbidae 



lip thickened and expanded, white, bordered by reddish band inside. 

 Parietal wall with white callus. 



Shell Maximum Aperture Aperture 



Height Diameter Height Diameter 



6.5 11.7 5.5 3.3 Holotvpe 

 6.1 12.0 5.1 3.0 Paratvpe 



6.6 11.6 5.5 3.3 Paratype 



Type Locality. Brook at Great Falls, Virginia. Collected by Soelner. 



Type Material. Holotvpe and seven paratypes, deposited in the United 

 States National iMuseum, Accession no. 227858. Holotvpe figured on plate 

 83, fig. 19; paratypes figs. 20-22. 



This variety may be distinguished by its small axial height, depressed 

 shape, wide and shallow spire depression, flat basal whorls with carina 

 near periphery. It resembles the variety poUtum from Canada, but that 

 variety has rounded basal whorls without marked carina, its spire depres- 

 sion is wide with more flat-sided whorls, and dorsal carina is more acute. 

 The basal part of the aperture is rounded or almost flat in politum, but has 

 sharp, wide angle in bartschi. 



Bartschi differs from sayi in lower axial height, less sharply angled 

 basal whorls (with carina not near edge as in sayi) ; shallow and wide 

 spire depression. 



Bartschi differs from anceps in lower relative axial height (compared 

 with diameter) ; wider spire depression; basal whorls flatter; carina nearer 

 periphery (near center in anceps). 



Helisoma anceps bartschi is apparently a common form in the Potomac 



drainage. 



Helisoma anceps idahoense. New Variety 



Plate 84, figs. 26-28 

 Plate 101, figs. 11, 12 



Spire with carina in center. Base concave, basal whorls flat to sutures 

 which are well marked. Whorls four. Spire depression deep and funnel- 

 shaped, the whorls flat-sided. Carina well marked. Whole shell is cone- 

 shaped, the whorls sloping upward to the spire carina. Color yellowish horn. 

 Sculpture of regular growth ribs crossed by distinct spiral lines. Aperture 

 auriform (reversed), sharply angled above, flat or flatly-rounded below. 

 Lip sharp. Distinct columellar callus. Color of aperture whitish or slightly 

 purplish. A callus often within the lip edge. 



There is considerable variation in width and depth of spire depression. 

 Base rarely rounded, without carina. Carina always near center of base. 

 Some variation in shape of aperture. It may form a sharp V below (as in 

 the holotype) or it may be rounded and flattened at this point. This- variety 

 is nearest to latchfordi, differing in the less angular basal portion of the 

 aperture and also in the more distinct and heavier spiral sculpture in 

 idahoense. 



