7 
the western part of the upper peninsula of Michigan as none has been 
collected from the lower part of the upper peninsula by recent collecting 
parties. The writer has collected extensively in northern Wisconsin and 
did not find corpulentum. It is quite possible that the Michigan specimens 
really came from Minnesota and were collected by an early survey party 
that failed to specify the exact locality. Until additional specimens are 
found in Michigan this record must be looked upon with suspicion. Its 
presence in northern Minnesota in abundance is without question. 
The range of typical corpulentum, as judged by the available records, 
is from the southeastern corner of Manitoba eastward to Minnitaki lake, 
Thunder Bay district, Ontario, and from Trout lake, Patricia portion of 
Kenora district, Ontario, southward to Itasca State park in Clearwater 
county, Minn. Dali’s and Walker’s record from lake Vermilion, Alberta, 
in latitude 56° 30', leaves a wide stretch of territory (about 750 miles) 
without records. Dali evidently included this record from Walker’s paper 
(1900), in which the specimens are said to have been in the James Lewis 
collection, the collector being unknown. The specimen figured, which 
is in the Walker collection, is so like an immature specimen of the race 
vermilionense that one is led to wonder whether or not Vermilion lake, 
Minnesota, was not the locality rather than the lake in Alberta so many 
miles from the other records of corpulentum. This record of the species 
must be open to question until authentic material from the intervening area 
has been obtained. 
Helisoma corpulentum vermilionense F. C. Baker 
Plate I, figures 8-13; Plate IV, figures 5-8 
Helisoma corpulenta vermilionensis F. C. Baker, Nautilus, XLII, page 
131 (1929). 
Planorbis corpulentus Grant, Ann. Rept., Geol. and Nat. Hist. Surv. 
Minn., 16, page 484 (1887); Walker, Nautilus, XIII, page 136 
(part), PI. iii, figs. 4-6 (1900). 
Helisoma corpulenta F. C. Baker, Trans. Am. Micr. Soc. XLVIII, 
pages 44-46 (part), PI. viii (1929) ; Fresh Water Moll. Wis., I, PI. 
xix, figures 38-39 (1928). 
Shell differing from typical corpulentum in having the whorls at the 
shoulder and base encircled by a sharp, cord-like carina which persists to 
the aperture both above and below, the spire much flatter, the umbilicus 
relatively deeper, and the base of the shell much flatter; the axial height 
is greater and the aperture is higher and narrower, and peculiarly effuse 
and expanded below; the body whorl is more flat-sided in the race, in many 
specimens being concave, hence modifying the aperture to a considerable 
degree. In most specimens the new whorl is so tightly appressed to the 
preceding whorl as to form a marked plait on the columella, which is not- 
ably conspicuous on immature shells (See Plate IV, figures 5, 6). The 
sculpture of the surface is usually coarse like that of the typical form, but 
specimens occur with the fine sculpture of multicostatum ( See Plate I, 
figure 13). 
