10 
in the multicostatum race. The radula formulae of the related species and 
races also differ somewhat, as noted below: corpulentum 32-1-32 to 41-1-43 ; 
vermilionense 25-1-25 to 29-1-29; multicostatum 35-1-35 to 43-1-43; pilsbryi 
27-1-27 to 29-1-29. 
Multicostatum has been confused with typical corpulentum and its 
geographic range cannot be ascertained from the literature without an 
examination of the specimens upon which the older records of corpulentum 
were based. Such examinations have been made wherever the material 
was available. The material examined, together with that collected by 
Dr. Cahn, provides the following records for this race: 
National Museum, Canada, 2221. Root river, coll, by Wm. Mclnnes, June, 1904. 
Acad. Nat. Sci. Phil., 141906. Cherry island, Rainy lake, Ontario. 
Mus. Zool., Univ. Mich., 49737. Lake Plantagenet, near Bemidji, Hubbard 
county, Minn. 
ITS. Nat. Mus., 251142. Cherry island, Rainy lake, Ontario. 
Univ. 111., Z32306-8. Kahnipiminanikok lake, Rainy River district, Cahn coll. 
Univ. 111., Z30865. Hill lake, Kenora district, Cahn coll. 
Univ. 111., Z30S64. Birch lake, Patricia portion of Kenora district, Cahn coll. 
Univ. 111., Z30863. Lake St. Joseph, Patricia portion of Kenora district, Cahn coll. 
Univ. 111., Z32332. Swamp of lac des Mille Lacs, Thunder Bay district, Cahn. coll. 
Univ. III., Z32326. Sturgeon lake. Thunder Bay district, Cahn coll. 
Univ. 111., Z30866. Abram lake, Thunder Bay district, Cahn coll. 
Univ. 111., Z29828. Knife lake, St. Louis county, Minn., Cahn coll. 
Univ. 111., Z32336. Fall lake, St. Louis county, Minn., Cahn coll. 
Univ. 111., Z32473. Mississippi river between Cass and Bemidji lakes, Beltrami 
county, Minn., Mus. Zool. Univ. Mich. 
Baker coll., 2783. Leech lake, Cass county, Minn., Prof. Sam. Eddy. 
Multicostatum, therefore, is distributed from Birch lake, Out., south- 
ward to Leech lake, Cass county, Minn., and eastward in Ontario to lake 
St. Joseph, Its geographic range is thus about the same as that of typical 
corpulentum in both Ontario and Minnesota. 
Helisoma whiteavesi F. C. Baker 
Plate II, figures 1-5; Plate IV, figures 13, 14 
Helisoma whiteavesi F. C. Baker, Nautilus, XL VI, p. 7 (1932) . 
Shell strikingly heterostrophe, of whorls, slowly increasing in dia- 
meter; spire consisting of the whorls coiled in the same plane forming a 
truncated upper surface; base of shell flattened, the umbilicus deep, the 
base showing only two fully formed whorls; a carina encircles both the 
shoulder and the basal part of the whorls; aperture ear-shaped, higher than 
wide, angled above, rounded below; the lip is reflexed; the aperture may be 
chocolate coloured within or the outer lip may be margined by a dark band; 
the sculpture is of distinct, rather evenly spaced riblets, the spaces being 
twice as wide as the riblets. 
H.19‘0; Gr. diam. 24-0; Ap.H. 15-5; D.9-0 mm. Holotype, U.I. coll. Z323U. 
H.18-2; Gr. diam. 23-2; Ap.H. 15*0; D.9-0 mm. Paratype. U.I. coll. Z32312. 
H.18-8; Gr. diam. 21*5; Ap.H. 14*2; D.8-1 mm. Paratype. U.I. coll. Z32312. 
H.12-0; Gr. diam. 10*4; Ap.H. 11*5; D.5-0 mm. Paratype. U.I. coll. Z32312, 
Type Locality. Lac des Mille Lacs, Thunder Bay district, Ontario. 
