208 THE CHICAGO ACADEMY OF SCIENCES. 



Genitalia: See generic description. 



Distribution: Eastern and Central United States, and Can- 

 ada; west to Minnesota. 



Geological distribution: Pleistocene of the Mississippi Val- 

 ley; Loess. 



Habitat: Very abundant under logs, underbrush, and in 

 crevices or under loose bark. Sometimes found buried in the 

 earth. Dry situations are not favorable to it, and it prefers 

 moist localities in wooded districts. 



Remarks: This is our most abundant species, and, unlike 

 most of our Helices, is gregarious, being generally found in 

 colonies of from twenty to a hundred or more. The animal is 

 sluggish in its movements, but is not at all shy, allowing itself 

 to be picked up and examined without withdrawing into its 

 shell. Its locomotion is slow and careful. The species is very 

 variable in the height of its spire, some specimens having an 

 elevated, convex spire, while others are perfectly flat. This 

 variation is in a great measure due to the habit of crowding 

 itself into narrow crevices, which causes the shell to assume a 

 flat-whorled aspect. The convex forms are generally found 

 in wide, open crevices or under logs, while the flat-whorled 

 forms are found in small, narrow crevices or under loose bark. 

 The albino form is found very sparingly. The measurements 

 and figures show well the variation in the spire. The striation 

 of the species varies from almost smooth (Jergusoni) to very 

 coarsely ribbed (mordax). It is fond of climbing trees and is 

 often found at a considerable height from the ground. 



Egg laying begins about the first week in June and the an- 

 imals are then in their best condition. From twenty to eighty 

 pure white, opaque eggs are laid, agglutinated together in soft 

 clay (Fig. 22). About thirty days are required for them to 

 hatch, and about the middle of July young snails are found 

 with two perfect whorls. The eggs measure 2.75 mill, in diam- 

 eter and when dry become hard and brittle. 

 80. Pyramidula solitaria Say, pi. xxix, fig. 1. 



Helix solitaria SAY, Journ. Phil. Acad., Vol. II, p. 157, 1821. 



Pyramidula occidentalis VON MARTENS. 



Pyramidula solitaria limitaris DAWSON. L. and F. W. Moll. coll. Sum- 

 mers, 1873, 1874, pp. 347-350, 1875. 



Patula solitaria albina W. G. BINNEY. 



Shell: Depressed-globose, rather solid, diaphanous, deeply 

 and widely umbilicated; surface slightly shining, covered with 

 coarse, crowded, oblique striae; color dark horn, with two re- 



