538 PROCEEDINGS OF THE ACADEMY OF [DeC, 



Mrs. George Andrews informs us that no specimens from east of the 

 Mississippi have come to her knowledge aside from the records in Mr. 

 Binney's work, already alluded to. 



It is our experience that in the trans-Mississippian region where P. 

 dorfeuilliana occurs it is a common snail, readily found in all suitable 

 stations, and often in considerable quantity. It is not one of the 

 snails occurring only in restricted localities and requiring special search 

 to find. It seems therefore doubtful whether its range really extends 

 east of the Mississippi at all; and until some definite cis-Mississippian 

 locality for it is put on record, we are disposed to erase Ohio, Kentucky, 

 Tennessee and Alabama from the ascertained range of the species. 



The variety percostata Pils.^** (PI. XX, fig. 23) was based on 

 specimens from the Red River in southwest Arkansas, in which the 

 riblets of the upper surface continue over the base, which is strongly 

 and coarsely rib-striate. The sculpture, however, varies a good deal, 

 even in the original lot of several hundred specimens, most of which 

 are as smooth as the ordinary form of dorfeuilliana. The umbilicus, 

 while variable in width, is never so wide as in typical sampsoni. The 

 diameter is from 7 to 9 mm. 



We hesitate now to treat P. d. percostata as a subspecies, yet the 

 tendency in this local race to produce a sculptured base is not present 

 in a great number of other colonies of dorfeuilliana which have been 

 studied in thousands of specimens. 



P. d. perstriata n. subsp. PI. XX, figs. 24 (type), 20, 21, 22. 



Another incipient race of P. dorfeuilliana from Tushkahoma and 

 Poteau, Indian Territory, is open below like P. d. sampsoni, but the 

 base is finely and densely striate. In a large series collected the 

 sculpture varies but little. 



Other specimens from Mena, Ark. (PI. XX, figs. 20-22) are smaller, 

 and vary to forms with less distinctly striate base. 



Polygyra jaoksoni (Bland). PI. XX, figs. 1-5. 



The axis in this species is distinctly perforate at all stages of growth. 

 The upper lip-tooth is deeply placed and very oblique. Viewed from 

 the inside, the spire and parietal wall removed, it is seen to be 

 a narrow oblique lamina. There is no tubercle on the columella inside, 

 at least in the specimens I have opened. The diameter varies ordi- 

 narily from 6.5 to 7.5 mm. 



The type locality is Fort Gibson, I. T. We collected it copiously ^in 



*" Polygyra dorfeuilliana percostata Pils., Nautilus, XIII, p. 37. Type loc.jnear 

 Texarkana, Ark., on the Red River. 



