LYMNAIDA OF NORTH AMERICA. i, 373 
the whorls very convex (pl. XXXIX, fig. 13). The Alaska speci- 
mens do not differ materially from those collected in Greenland. 
Galba vahlii was first mentioned by Beck in his index, but was 
not described.. Méller described it in his index and Morch both de- 
scribed and figured it in American Journal of Conchology, Volume 
IV. Authentic specimens received from Mérch have been examined 
both in the Academy of Natural Sciences of Philadelphia and in the 
Smithsonian Institution. These compare favorably with the speci- 
mens described and figured in this monograph. 
It has not been possible to successfully differentiate the varieties 
indicated by Mérch in his review of the Greenland fresh-water mol- 
lusks, in the American Journal of Conchology. All seem to be minor 
variations of one type of shell. Variety /ewcostoma is said by Morch 
(Amer. Journ. Conch., p. 34) to be “somewhat smaller and broader 
than the type, but differs chiefly by a thick layer of milk-white chalk, 
which covers all the inside and columella, giving the exterior of the 
shell a light straw color.” This last character is not constant in any 
large series, besides being a physiologic character. The form minor 
of this variety (1. c., p. 34) is also a very trivial variation not worthy 
of a distinct name. The shell of vahlit is seen to vary from short to 
long spired when a number of specimens are examined. Varieties 
parva and nitens appear to be local mutations of vahlii as do also 
wormskioldi Beck and malleata Morch. 
An examination of the axis of vahlii shows it to be placate and 
a member.of the Stagnicola group instead of the Galba group, as in- 
dicated by Dr. Dall. 
Galba vahlii arctica (Lea). Plate XXXIX, figures 19-23. 
Lymnaea arctica LEA, Proc. Phil. Acad., p. 113, 1864; Journ. Phil. Acad., 
VI, p. 160, pl. 24, fig. 75, 1866; Obs., XI, p. 116, pl. 24, fig. 75, 1867.—SCUDDER, 
Bull. Nat. Mus., 23, pp. 147, 200, 1885. 
Limnea arctica Tryon, Con. Hald. Mon., p. 100 (74), pl. 17, fig. 9, 1872. 
Limnophysa arctica Tryon, Amer. Journ. Conch., I, p. 255, 1865. 
Limnea vahlii Wuiteaves, Nautilus, XIX, p. 4, 1905; Ottawa Nat., SEES 
p. 66, 1905. 
SHELL: Thick and solid, opaque, oblong-ovate ; periostracum dark 
horn or chestnut, sculpture as in vali; many of the specimens ex- 
amined have a rather thick epidermis which hides the sculpture of the 
shell; whorls 5%, convex, rather rapidly increasing in size; sutures 
well marked but not deeply impressed ; spire short, acutely pyramidal, 
about as long as the aperture; the spire whorls are inclined to be 
shouldered, and the fourth and fifth whorls are disproportionately 
enlarged; aperture ovate, dark colored within ; outer lip thickened near 
