552 PROCEEDINGS OF THE ACADEMY OF [DeC, 



Arkansas: Rogers, Benton Co. (F. & P.); Eureka Springs, Carroll 

 Co. (S.); Blue Mt. Station and Magazine Mt., Logan Co. (F. & P.); 

 Carrion Crow Mt., Pope Co. (F.) ; Petit Jean, Yell Co. (F.) ; Hot Springs, 

 Garland Co. (F., S.) ; Mablevale, Pulaski Co. (C. W. Johnson) ; Washita 

 Springs (Gould, type loc); also reported from Crawford, Franklin, 

 Sebastian and Conway counties (S.). 



Indian Territory: Fort Gibson, in the Cherokee country (E. W. Hub- 

 bard, C. T. Simpson). 



Louisiana: Grand Cane, De Soto Parish (Williamson). 



P. divesta has been reported from Bowling Green, Ky., by Miss S. F. 

 Price {Nautilus, XIV, 75), but I have not seen specimens from there and 

 am not sure of the identification. It has also been recorded from 

 "Vernon Co., Miss.," but there is no county of that name in the State. 

 No reliable record of its occurrence east of the Mississippi River exists. 



Throughout its range the species is very uniform in character, the 

 diameter ordinarily being from 17 to 21 mm. At Chadwick, where 

 nearly all land snails are dwarfed, the shells are remarkably small, a 

 series of 23 measuring as f oUows : 



No. of specimens 1 3634411 



Diam. inmm 13.6 14.5 15 15.5 16 16.5 17 18 



Polygyra albolabris alleni (Wetherby). 

 Proc. A. N. S. Pliila., 1903, p. 197. 



Several small series were taken in 1903 showing variations similar to 

 those discussed in a former paper. Aside from size the shells do not 

 vary much. The diameters are tabulated below for ten localities 

 where we took the species in 1903. 



Two large specimens from the north side of Magazine Mountain show a 

 parietal tooth. We do not remember seeing this tooth developed in 

 the trans-Mississippian race of albolabris hitherto. 



The largest specimens were taken on steep, damp and rocky northern 

 slopes, without reference to elevation. At Wyandotte, at an elevation of 

 about 900 feet above the sea, they Uve on the steep, rocky bluff facing the 

 river. At Magazine Mountain the series of large shells came from the 

 edges of the talus, just under the great sandstone cliff along the northern 

 side of the pleateau summit, at an elevation of about 2,700 feet; while 

 at an equal elevation on the dry south side, with the same sort of rock 

 and abundant cover, the shells were small, 25 mm. diam., and at the 

 base of the mountain still smaller, 24.5 mm. At Chadwick, where the 

 country rock is limestone, the individuals are small, 22 to 25 mm. 



The size of individuals in this species and area seems to be dependent 

 upon the abundance of cryptogamic food, and is therefore a function of 



