11 
Types. Holotype and paratypes, U.I. coll., Z32311, 32312. Para- 
types: Nat. Mus., Canada, No. 3223; Acad. Nat. Sci. Phil., 158591. 
Collected by A. R. Cahn. 
Whiteavesi is distinguished from all other members of the corpulentum 
group by its flat spire, great axial height, and deep umbilicus in which only 
two full whorls may be seen. The sculpture is coarser than in the race 
multicostatum , but finer than in the typical corpulentum. It is with some 
hesitancy that this striking form is made a distinct species, for it is 
obviously a member of the corpulentum group. However, no individual in 
the rather large number of specimens of corpulentum and its races ex- 
amined has shown a tendency to vary toward this form and the lot of 
whiteavesi material is so constant in its characteristics that it is deemed to 
be of specific rank. This fine species is dedicated to the deceased Canadian 
naturalist, Dr. J. F. Whiteaves, who did so much to advance the knowledge 
of the molluscan fauna of Canada. 
The geographic distribution of whiteavesi is unknown. The type 
locality, lac des Mille Lacs, is in Thunder Bay district, Ontario, where it is 
apparently common. Three specimens in the National Museum, Canada, 
from Greenwater lake, about 15 miles south of lac des Mille Lacs, appear to 
be referable to whiteavesi. Although this species is at present unknown 
beyond its typical locality region in Thunder Bay district, there is every 
reason to believe that its distribution will be widely extended, unless the 
species be one of the products of post-glacial evolution of limited distri- 
bution, as appears to be the case with some of the freshwater pulmonates. 
It is a curious parallel that the radula formula of whiteavesi is exactly 
like that of typical corpulentum , 36-1-36 to 41-1-41. Immature shells of 
whiteavesi are different from those of corpulentum, vermilionense, or 
multicostatum (See Plate iv, figures 13-14). In axial height they most 
nearly resemble the immature form of vermilionense (Plate iv, figures 5-6). 
Group of Helisoma trivolvis 
Helisoma trivolvis (Say) 
Plate III, figures 1-8; Plate IV, figures 17-19 
Planorbis trivolvis Say, Nicholson’s Ency., 1st. Ed., II (no pagina- 
tion), PI. ii, fig. 2 (1817) ; Am. Conch., VI, PI. 54, fig. 2 (1834) ; 
Binney, Writings of Thomas Say, p. 44, PI. 54, fig. 2 (1858) ; Land 
and F.-W. Shells N.A., II, p. 115, fig. 194 (1865). 
Helisoma trivolvis (Say), Baker, Fresh Water Moll. Wis., I. p. 330, 
PI. xx, figs. 1-6 (1928). 
Planorbis trivolvis has been made a “dumping ground” for nearly 
every Planorbis-like shell of the United States and Canada from the 
Atlantic to the Pacific, and the various forms referred to this protean 
species probably include nearly all of the larger species. Say’s original 
locality was French creek, a tributary of Allegheny river, this being the 
only locality given in the original description. As this creek rises in 
Chautauqua county, N.Y., and passes into Erie county, Pa., the original 
