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. totteniana Lea, 

 (pi. 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 ovalis. The radula and jaw 

 are similar to those of ovalis. 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 in hibernation, withdrawn so far within the shell that half of 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 obliqua. The writer believes, with Mr. 

 Bryant Walker, that the elder Binney had no authority for 

 using obliqua 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, pi. xxx, fig. 24. 



Succinea retusa LEA, Trans. Amer. Phil. Soc., Vol. V, p. 117, pi. xix, 



fig. 86, 1837. 



Succinea ovalis GOULD, Invert. Mass., p. 194, fig. 125, 1841. 

 Succinea forsheyi LEA, Proc. Phil. Acad., p. 109, 1864, Obs., Vol. XI, 



p. 134, pi. xxiv, fig. 107. 



Succinea ivilsoni LEA, 1. c., Obs. 1. c., fig. 105. 

 Succinea decamfii TRYON, Amer. Journ. Conch., Vol. II, p. 237, pi. ii, 



fig. 23, 1866. (Variety.) 

 Succinea calumetensis W. W. CALKINS, Valley Naturalist, Vol. I, No. 



2, p. 1, fig. St. Louis, Nov., 1878. 

 Succinea peoriensis 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, 



