1903.] NATURAL SCIENCES OF PHILADELPHIA. 197 



race in which the teeth are much reduced, though still the Hp-teeth are 

 decidedly stronger than in P. edentata. Specimens measure — 



Alt. 5.3, diam. 11.5 mm.; whorls 4f. 



Alt. 5, diam. 9.5 mm.; whorls 4^. 



The last whorl is somewhat more costulate behind the lip than usual 

 in P. inflecta. This form may be called var. media. 



P. inflecta was taken also at Rich Mountain,* Hot Springs* and 

 Carrion Crow Mountain,* Ark.; Tushkahoma* and Standley,* I. T. 

 Polygyra edentata (Sampson). 



Chester, Crawford county, western Arkansas. Two specimens sent 

 measure 12 and 14 mm. diam., and have 5 and 5^ whorls. Eighteen 

 were taken at this locality. 



Polygyra albolabris alleni iWetherby). 



Mesodon albolabris Say, and var. minor A. G. Wetherby, Some Notes on 

 American Land Shells, No. II, in Joum. Cincinnati Soc. Nat. Hist., IV, 

 p. 11, December, 1881. Eureka Springs, Carroll county. Ark. 



M. albolabris Say, F. A. Sampson, Bull. No. 1, Sedalia Nat. Hist. Soc, p. 19, 

 1885. Sedalia, Mo. 



Mesodon albolabris Say. var. alleni (\Vetherby) and var. minor Sampson, 

 MoUusca of Arkansas, in Ann. Rep. Geol. Surv. of Ark., II, pp. 189, 190, 

 1893. Carroll, Benton, Sebastian, Crawford, Garland, Washington, 

 White, Johnson, Nevada, and Independence counties. Ark. 



Polygyra albolabris alleni Weth., Pilsbry, in these Proceedings for 1900, 

 p. 451. Iowa and Arkansas. 



All of the above references pertain, I believe, to a single widespread 

 race of P. albolabris, varying in size and color almost as much as the 

 Eastern form of the species, but in a broad view distinguishable from 

 the latter by one, several or all of the following characters : The shell 

 is thinner, more depressed and more glossy; the spiral lines and other 

 minute sculpture are weaker; the lip is narrower, rounded rather than 

 if at, with a weaker less angular rib within; the low basal tooth is fre- 

 quently more distinctly defined. Distribution, west of the Mississippi 

 from southern Minnesota to Arkansas, and eastward in the South to 

 Jackson county, in northern Alabama. 



In the North, P. albolabris replaces alleni east of the Mississippi river, 

 in Illinois. I have seen typical P. albolabris from west of the Missis- 

 sippi only from Winfield, Henry county, in southeastern Iowa, where 

 it coexists with var. alleni. Owing to the frequent cutting of "ox- 

 bows" by the Mississippi, and the consequent transfer of islands from 

 one to the other side of the stream, even that great river is no bar to 

 the distribution of snails inhabiting lowland forests; and somewhere 

 a,long the immediate vicinity of the Mississippi the areas of albolabris 

 and alleni probably overlap, with perhaps a belt of undifferentiated 

 intermediate forms. 



