8 
H.15-0; Gr. diam. 21*5; Ap.H. 16-0; D.12-0 mm. Holotype. Baker coll. 3019. 
H.14*G; Gr. diam. 22-0; Ap.H. 15-5; D.12*0 mm. Paratype. Baker eoll. 3020. 
H.13-5; Gr. diam. 17*5; Ap.H. 13 * 0 ; D. 9*5 mm. Paratype. Baker coll. 3020. 
H.12-0; Gr. diam. 13*5; Ap.H. 11*0; D. 9*0 mm. Paratype. Baker coll. 3020. 
H. 8*0; Gr. diam. 10*0; Ap.H. 7*9; D. 5*5 mm. Paratype. Baker coll. 3020. 
Type Locality. Vermilion lake, St. Louis county, Minn. Birch point. 
Types. F. C. Baker coll., as above. Paratypes: Nat. Hist. Mus., 
U. of I., Z32518; Acad. Nat. Sci. Phil., 147370. 
The same characteristics that separate vermilionense from corpulentum 
will distinguish it from the race multicostatum, from which it differs also 
in its coarser sculpture. Although the base of multicostatum is more 
flattened than in the typical corpulentum , it is never concavely flattened 
and with the sharply angled peripheral edge of vermilionense. Immature 
shells differ tvidely and are compared on Plate IV, figures 1 to 4 and 5 to 8. 
The geographic range of this race is unknown at present. If is very abund- 
ant in Vermilion lake, Minn., and is, apparently, the only large Helisoma 
found in the lake. The specimen figured by Walker (Nautilus, XIII, 
PI. iii, figure 7) and stated to be from Vermilion lake, Alberta, looks very 
much like vermilionense, and the record may be an error for Vermilion 
lake, Minn. It was in the James Lewis collection, acquired by Dr. Walker, 
and the collector is unknown. Until the record is substantiated by fresh 
specimens it must remain in question. It appears, then, that as far as 
authentic material is concerned the race vermilionense is confined to the 
Vermilion Lake region. It was not found by the Cahn parties in western 
Ontario. 
Helisoma corpulentum multicostatum F, C. Baker 
Plate I, figures 14-20; Plate IV, figures 9-12, 21 
Helisoma corpulentum multicostatum F. C. Baker, Nautilus, XLVI, 
page 7 (1932). 
Shell differing from typical corpulentum in having the rib-strise finer 
and more numerous, there being three or four riblets in the space of a 
millimetre; the base is flatter w r ith a well-developed carina on the edge of 
the basal whorls; the base exhibits three full whorls, whereas in corpulentum 
only two and a fraction are visible; the shell is normally larger with about 
half a whorl more than in the typical form. 
H, 13*8; Gr. diam. 24*0; Ap.H. 11*8; D. 8*0 mm. Holotype. 
H. 15*5; Gr. diam. 29*5; Ap.H. 13*0; D. 8*5 mm. Paratype. 
H. 14*0; Gr. diam. 26*8; Ap.H. 11*5; D. 7*7 mm. Paratype. 
H. 13*5; Gr. diam, 20*0; Ap.H. Ill* 1 ; D. 6*6 mm. Paratype. 
H. 11*0; Gr. diam. 15-5; ApLT, 10*1; D. 5*5 mm. Paratype. 
U.I. coll. Z32306. 
U.I. coll. Z32307. 
U.I. coll. Z32307. 
U.I. coll. Z32307. 
U.I. coll. Z32307. 
Type Locality. Kahnipiminanikok lake, Rainy River district, 
Ontario. 
Types. Holotype, paratypes, U. of I. coll, as above. Paratypes: Nat. 
Mus., Canada, No. 3216; Acad. Nat. Sci. Phil., 158592. 
