1910.] NATURAL SCIENCES OF PHILADELPHIA. 21 



VARIATION OF POLYGYRA ALBOLABRIS IN MICHIGAN. 

 BY BRYANT WALKER. 



Polygyra albolabris Say is not only the largest, but one of the most 

 abundant and widely distributed species of the genus. It inhabits 

 the whole of the Eastern States and Canada, ranging north to the 

 Saskatchewan, south to Florida and west to Nebraska, Kansas and 

 Texas. It may be fairly said to be the characteristic land snail of 

 the region. 



In view of the enormous extent of territory which it occupies, and 

 the very diverse environmental conditions to which it is subjected, 

 it would naturally be expected to show a very considerable range of 

 variation. This Is true particularly in the Southern States, where 

 in the southeast two well-marked varieties {major Binn. and fusco- 

 labris Pils.) have been developed, and in the southwest a third (allcni 

 Weth.), which practically replaces the typical form west of the Missis- 

 sippi from Missouri to Texas. 



In the region north of the valley of the Tennessee River and east 

 of the Mississippi, however, the typical form is everywhere present 

 and, except in size and contour, presents no substantial variation. 



Barring var. dentata Tryon, a dentate form, and var. fusca Billings, 

 a color variation, which do not come within the province of this paper, 

 the only varieties to receive recognition have been based mainly on 

 size. There have been three of these to appear in the literature, of 

 which only one has been fully described, viz.: var. mariiima Pils. 1 

 from the New Jersey coast. Var. minor Sterki 2 from New Philadel- 

 phia, O., is simply stated to be "a peculiar, small, thin-shelled form." 

 While var. traversensis Leach 3 was never described at all, but was a 

 MSS. name attached to a small form collected by Leach near Traverse 

 City, Michigan, which is stated by Pilsbry 4 to be "scarcely distin- 

 guishable" from var. mariiima. 



In the preparation of the writer's Illustrated Catalogue of the Mollusca 



1 Proc. Acad. Nat. Sci. Phila., 1890, p. 283. 



2 L. and F. W. Mollusks of New Philadelphia, O. (1S94). The var. minor of 

 Wetherbv (1881) and of Sampson (1893) are referred to var. allcni Weth. by 

 Pilsbrv, Proc. Acad. Nat. Sci. Phila., 1903. p. 197. 



3 Manual of Conch., IX, p. 76 (1894). 



4 Cat. Land Shells of Am. (1898). 



