20 
V-shaped angle above; outer lip not reflected, or only very slightly reflected 
in some individuals; parietal wall with only a slight wash of callus; 
aperture brownish within. 
H.15*0; Gr. diam, 27-5; Ap.H. 14*5; D.9-0 mm. Bolotype, Baker coll., 846. 
H.15-0; Gr. diam, 26-0; Ap.H. 15*5; D.9-5 mm. Paratype, Baker coll., 843. 
H.14-0; Gr. diam. 26-0; Ap.H. 13*0 ; D.8*0 mm. Paratype, Baker coll., 843. 
Type Locality. Tomahawk lake, Oneida county, Wis. 
Types. Baker collection, as above; Acad. Nat. Sci. Phil., 140269. 
Helisoma pilsbryi proves to be another composite species including in 
its references large specimens of trivolvis and especially the recently 
recognized species injracarinatum. The rounded, uncarinated whorls of the 
base are its principal distinguishing feature, differing widely in this respect 
from the new form called infracarinatam in which at least the inner basal 
whorls are always carinated. • The rounded whorls of pilsbryi will at once 
distinguish it from any member of the corpulentum complex. In previous 
references the author has considered this form to be a variety of the 
common trivolvis. But the form of the shell is sufficiently characteristic, 
it would seem, to consider pilsbryi another form allied to trivolvis and 
injracarinatum. The radula formula ranges from 27-1-27 to 29-1-29, 
whereas that of trivolvis ranges from 22-1-22 to 26-1-26. The previous 
record (Fresh Water Moll. Wis., p. 334) of 23-1-23 for pilsbryi was an 
error, four different membranes examined with high powers gave not less 
than 27 nor more than 29 teeth on each side. The specimens were from 
Chetek region in Wisconsin. 
Geographically, pilsbryi is distributed from New Brunswick westward 
to Wisconsin and northward to the vicinity of the Canadian boundary. 
The records upon which this distribution is based are as follows: 
In Nat. Hist. Museum, U.I., Tomahawk lake, Oneida county, Wis. (Z29138, 
29139) ; Chetek lake, Prairie lake, Taber lake, Barron county, Wis. (Z13482, 13485, 
13496, 13527, 13538), collected by F. C. Baker; Plum lake (25129), Star lake (29916), 
Nixon lake (23130), outlet Big Johnson lake (23128), Vilas county, Wis., collected by 
A. R. Cahn; Little Arbor Vitae lake, Vilas county, from Wis. Geol. Nat. Hist. Surv. 
(Z18630) ; first lake on Green river, Restigouche district, New Brunswick (Z32479), 
collected by O. O. Nylander; Baker collection as follows: 
Oneida lake, New York (863), Cazenovia lake, Madison county, N.Y. (850). 
Meach lake, Quebec, Canada (LaRocque). 
The states from which authentic specimens are represented are New 
York, Michigan, Wisconsin, and Minnesota. It is apparently rare in 
Canada, the only specimens seen being from New Brunswick and Meach 
lake. All material from Canada previously referred to pilsbryi is now 
referable to injracarinatum. Pilsbryi appears to occupy a strip of territory 
in the United States somewhat south of the International Boundary. It 
will probably be found in some of the lakes immediately north of the 
boundary. 
