316 THE CHICAGO ACADEMY OF SCIENCES. 
precarious environment. The specimens from Thunder Bay Island ex- 
hibit admirably the effect of the heavy seas of Lake Huron, 
REMARKS: Alpenensis may be distinguished by its solid, narrow 
shell, long, acute spire, rounded whorls, with well rounded body whorl 
and particularly by its inner lip, which is wide and raised from the 
columellar region, producing an emarginate condition very similar 
to that in Galba emarginata. The solidity of the shell and particularly 
of the inner lip, which is nearly always continuous will also serve to 
aid in the identification of this race. Some small specimens somewhat 
resemble Galba palustris dcesidiosa, but that race is smaller, thinner, 
the spire is regularly turreted, the body whorl is proportionally wider 
and more obese and the inner lip is appressed to the parietal wall, pro- 
ducing a distinct plait. Galba elodes has a narrower shell with more 
flat-sided whorls and a more elongate aperture. 
This form is so numerous in individuals and so constant in char- 
acter that it seems necessary to bestow a name upon it as a race of 
palustris. Typical palustris from this locality lives in a still, swampy 
area which is protected from the rough waters of Lake Huron by a low 
shore. This quiet, peaceful habitat produces a large, thin shelled form 
quite unlike the race which lives on the exposed shore (see plate XX VI, 
figures 17-20; compare with figures on plate XX XIII). The environ- 
ment in this case has produced a shell which is uniformly so distinct as 
to be as easily distinguished as are any of the species of Lymne@a. At 
Halma, Minnesota, a narrow shell occurs, but this is connected by 
insensible degrees with the large corpulent form of typical palustris 
(see plate XX VI, figures 21-26). In Owasco Lake, N. Y., a narrow, 
long spired form occurs, but here again the variation runs into the 
typical form without a break. In alpencnsis, the peculiarities are quite 
uniform and there is no decided variation towards the large, corpu- 
lent form. Young shells have a short spire and elongate-ovate shape, 
but the fully adult shell is always as figured on the plate. The shells 
were collected by Dr. William A. Nason of Algonquin, [linois. 
Galba palustris desidiosa’ (Say). Plate XXXIV, figures 1-12. 
Lymneus desidiosus SAy, Journ. Phil. Acad., II, p. 169, 1821; Long’s Exped., 
II, p. 264, 1824; Binney’s Ed., pp. 66, 130, 1858. 
Limneus desidiosus Say, Amer. Conch., VI, p. 211, pl. 55, fig. 3, 1834; 
Binney’s Ed., p. 211, 1858. 
Limnea desidiosa Binney, L. & F. W. Sh. N. A., II, p. 48, 1865—Gou pn, 
Inv. Mass., p. 219, 1841 (part); Binney’s Ed., p. 470, 1870 (part). 
1Only those references are here given which are believed to refer to the 
true desidiosa. Several references listed under obrussa may belong here, but 
there appears to be no way of verifying them. 
