220 THE CHICAGO ACADEMY OF SCIENCES. 
Geological distribution: Pleistocene; Loess. 
Habitat: Found generally in moist localities, in the vicin- 
ity of some body of water, crawling on the grass and rushes 
along the margins. Also found on tree trunks to a consid- 
erable height, at some distance from water. 
Remarks: This is a species at once distinguished by its 
large size and peculiar oblique aperture. It is a very common 
mollusk and is found almost everywhere. At Bowmanville it 
has been seen on the bark of elm trees over five feet from the 
ground, where there was little or no moisture. There is some 
variation in the obliquity of the aperture, some specimens hav- 
ing the aperture long, narrow and straight. There is a form 
found at Bowmanville which approaches var. fottentana Lea, 
(pl. xxx, fig. 23); it is smaller, of a greenish tinge, and the 
aperture is more oval and less oblique; the animal is much 
darker, when alive, than typical ovals. The radula and jaw 
are similar to those of ovals. During the summer the animal 
is not able to withdraw completely into its shell, but as soon 
as winter approaches, the animal becomes smaller and is found 
in hibernation, withdrawn so far within the shell that half of 
the last whorl is empty. 
The species is universally distributed throughout the area. 
Students of the Mollusca will no doubt be surprised that 
ovalis is used in place of obligua. The writer believes, with Mr. 
Bryant Walker, that the elder Binney had no authority for 
using od/iqua instead of ovalis when the latter species has seven 
years’ priority. This being the case, the writer has used that 
name instead of obliqua. 
85. Succinea retusa Lea, pl. xxx, fig. 24. 
Succinea retusa LEA, Trans. Amer. Phil. Soc., Vol. V, p. 117, pl. xix, 
fig. 86, 1837. 
Succinea ovalis GOULD, Invert. Mass., p. 194, fig. 125, 1841. 
Succinea forsheyt LEA, Proc. Phil. Acad., p. 109, 1864, Obs., Vol. XI, 
p. 154, pl. xxiv, fig. 107. 
Succinea wilsont LEA, |. c., Obs. 1. c., fig. 105. 
Succinea decampi TRYON, Amer. Journ. Conch., Vol. II, p. 287, pl. ii, 
fig. 25, 1866.. (Variety.) 
Succinea calumetensis W. W. CALKINS, Valley Naturalist, Vol. I, No. 
2,p. 1, fig. St. Louis, Nov., 1878. 
Succinea peortensis WOLF, The Nautilus, Vol. VI, p. 19, 1892. (Variety.) 
Shell: Very ovate, elongated, thin, pellucid; surface cov- 
ered with very minute lines of growth; color very light horn 
or greenish-horn, sometimes tinged with rose; whorls three, 
PO, ha ae 
TAS -s - oh wee 
