LYMNZIDZ OF NORTH AMERICA. 425 
anteriorly a little accuminated ; columella thick, straight, outer lip with 
a single chestnut band within.” The Houghton Lake specimens were 
submitted by Mr. Walker to Mr. E. A. Smith of the British Museum, 
who compared them with Sowerby’s types and pronounced them identi- 
cal (see pl. XLIV. figs. 1-6). There is considerable variation in the 
form of the shell, as is the case with mighelsi, emarginata and can- 
adensis, the variation being the long or short spire, but all agree, when 
adult, in the tightly closed umbilicus, coarse sculpture, solid shell and 
angulated whorls. The Madison, Wisconsin, shells show a strong 
variation toward emarginata, and certain individuals might be referred 
to that species were it not that the majority of the specimens are of the 
angulata type. The shells from Minnesota appear to group with angu- 
lata rather than with typical emarginata, although isolated specimens 
might be referred to the typical form. Dr. Stearns (Proc. Nat. Mus. 
XXII, p. 136) records a large amount of variation in specimens from 
Eagle Lake, Minn., collected by Mr. Vernon Bailey. These vary in 
having a long or short spire, rounded or shouldered whorls, sutures 
deep or shallow, aperture patulous and distorted, surface malleated 
and shell rather solid or quite thin. The axis may be simple or rather 
strongly twisted. An examination of these shells, in the Smithsonian 
Institution shows them to belong to variety angulata, with a strong 
variation toward emarginata. Nearly all specimens agree in the tightly 
closed umbilicus although all are not angulated. 
The Michigan shells have been referred to both decollata and 
mighelsi. They are totally unlike decollata. From mighelsi they differ 
in the generally longer and narrower spire, rounder aperture, more 
angulated whorls, closed umbilicus and heavier texture. Specimens 
occur which might be referred to mighelsi, but on the whole the race is 
distinct enough to be differentiated from mighelsi, which has not been 
seen outside of Maine. Each race of emarginata contains many muta- 
tions which connect it with the typical form, but this 1s to be expected 
in a group of mollusks where polymorphism is as marked as in the 
fresh-water pulmonates. 
Galba emarginata wisconsinensis (Baker). Plate XLIV, figures 
10-18. 
Galba emarginata BAKER, Nautilus, XXIII, p. 113, 1910. 
Lymnea emarginata wisconsinensis BAKER, Nautilus, XXIV, p. 58, Sept., 
1910. 
SHELL: Very large, varying from elongated to globose, inflated, 
usually rather thin; periostracum varying from light yellowish horn to 
chestnut ; nuclear whorls as in emarginata; sculpture as in emarginata; 
