1903.] NATURAL SCIENCES OF PHILADELrHIA. 199 



southwestern Misso\iri and the Indian Territory, where in many 

 locaUties there is a very much wider variation in absolute size. Thu.s, 

 in a series of 18 shells from Sehgman, Barry covmtj'', southwestern Mis- 

 souri, the variation is from 20^ to 30^ mm.; the smallest being smaller 

 than the extreme of the Des ^loines lot of 50 shells, while about 

 70 per cent, of the shells are larger than the largest from Des 

 Moines. 



Of course no normal cur\-c can lie plotted from so small a series as 

 18 specimens; but in view of similar variation in other smaller lots, 

 the general features of the curve are indicative of the wide range of 

 individual variation. Tlie specimens in the present collection from 

 Missouri and Arkansas are as follows. There are not enough from an}^ 

 one place to make their variations of much significance, but I give the 

 data for what they are worth : 



De Soto, Jefferson county. Mo. A single thin, small specimen of 

 typical alleni, diam. 23 mm. 



Seligman, Barry count}', southwestern Missouri. See notes above. 

 Many of the specimens are large, 28 to 30 j mm. diam. 



Chester, Crawford county, Ark. Three specimens measuring 30, 

 26 and 23 mm. diam. The smaller ones thin, like maritima, the larger 

 one strong. 



Hardy, Sharp comity, northeastern Arkansas. Four specimens, 

 measuring 21, 22, 24 and 26 mm. diam. 



Hot Springs, Garland count}', Ark. A single specimen, diam. 29^ 

 mm., less depressed than usual. 



Rich ^Mountain, Polk county. Ark. Rather heav}', large specimens, 

 diam. 30 mm or more. 



Carrion Crow Mountain, Pope county. Ark. Diam. 24 to 27-j mm.; 

 rather light, with the usual narrow peristome. 



Tushkahoma, Choctaw Nation, I. T. Four large specimens only, 

 measuring 28^, 28^, 29A. 3H nun. diam. The spire is a little higher 

 than usual, and there are nearly ok whorls. The peristome is typical 

 of alleni. 



Standley, Choctaw Nation. A single shell similar to the above, 

 diam. 31 mm. 



In Kansas P. alleni occurs in Shawnee count}', and at Quenemo, 

 Osage county. The specimens resemble those from Iowa. None have 

 been seen from southwestern Arkansas or Texas. 



East of the Mississippi, specimens of typical alleni, resembling those 

 of Missouri, are in the collection of the Academy from near Decherd, 

 Franklin count}', in niiddlc Tennessee, near the Alabama boundary. 



