224 The Molluscan Fainily Planorhidae 



Helisoma kennicotti is a very distinct species. It differs from injra- 

 carinatum in its smaller size, greater relative axial height, as compared 

 with diameter. Expressed in percentages of height to diameter, kennicotti 

 is sixty-five per cent and infracarinatum, fifty-six per cent. The spire de- 

 pression is much smaller, narrower, and deeper in kennicotti, the shell 

 forming an inverted cone. The base of the new species is likewise narrower, 

 and the whorls dip into the umbilicus at a sharper angle, only one and 

 one-half turns before entering the umbilicus. In contrast, in infracarinatum 

 tliere are two full turns visible. 



Type Locality. Lake Isle la Crosse, English River, Canada. 



Type Material. Deposited in United States National Museum, Acces- 

 sion no. 29231, bearing the label of the old Binney collection no. 9272 and 

 there recorded as Planorbis trivolvis. Figures on jilate 89; holotype as 

 fig. 15; paratypes as figs. 16, 17; 13, 14 immature shells. 



Helisoma pilshryi prehlei. New Variety 



Plato 91, figs. 6 to 8 



Helisoma pilsbryi prehlei differs from typical pilsbryi in its greater relative 

 height in comparison with diameter of the shell. The whorls in prehlei are 

 more tightly coiled, the body whorl increasing more rapidly in diameter, 

 causing the spire depression and umbilical region to appear smaller than 

 in pilsbryi in which the whorls are rounded more regularly. The aperture 

 is widely expanded to form a reflected lip. This is not true of pilsbryi. 

 Whorls, four and one-half. Sculpture as in pilsbryi. H. p. preblei differs 

 from subcrenatum in absence of all indication of a carina on the umbilical 

 side. The whorls of the spire depression are subangulated, not sharply 

 angled as in infracarinatum. 



Height Diameter 



at at 



Expanded Expanded 



Lip Lip 



17.0 27.0 



16.0 26.0 



*Bioken specimen with four and one-fourth whorls, the last one-half whorl broken away. 



Type Locality. Knee Lake, Manitoba, Canada. 



Type Material. Three specimens, collected by E. A. Preble in the 'North 

 West Territory, Knee Lake, Keewatin,' deposited in United States National 

 Museum, Accession no. 180279. Figured on plate 91, holotype as fig. 6; 

 paratypes as figs. 7, 8. 



The type material was i:)reviously called infracarinatum but it is nearer 

 to pilsbryi. It differs from the latter in its expanded lip and more tightly 

 coiled whorls of the umbilical region. Differs from infracarinatum in the 

 absence of a basal carina and in having a narrower and more sunken 

 spire depression. 



Helisoma subcrenatum perdisjunctum^. New Variety 



Plate 96, figs. 13-17 



Shell small, horn colored; whorls three and one-half to four, discoidal, 

 evenly rounded; 3 whorls below. Whorls slowly increasing in diameter, 

 rounded above and below, not carinated. Sculpture of distinct growth lines, 



