532 PROCEEDINGS OF THE ACADEMY OF [DeC, 



those widespread forms of the whole CaroHnian zone, yet they have a 

 similar facies, owing to the rich development of Stenotrema and toothed 

 Zonitidce, the relative scarcity of Pupillidce, etc. It may be that the 

 resemblances are due to parallelism in evolution of the faunas from a 

 common source, yet the possibility may be entertained that the 

 Mississippi embayment, which isolates the Ozark uplift, was crossed 

 by a ridge, permitting rock-living snails to emigrate west from the 

 Cumberland plateau, at some period in tertiary time. This is a geo- 

 logical question aside from our present purpose.^ There is no mention- 

 able trace of Boreal zone elements in any of the three southern moun- 

 tain faunas ; and no ground exists in the molluscan fauna, for mapping 

 even the highest peaks as Canadian or Alleghanian. 



The Ozarkian fauna is thus one of several mountain faunas of com- 

 mon origin, all traceable to the Appalachian tertiary radiation. The 

 limits of this fauna can be mapped only after much more field investi- 

 gation, but roughly it includes the broken country of southern Mis- 

 souri, a small area in southeastern Kansas, the hilly eastern part of 

 Indian Territory, and the greater part of Arkansas, east as far pos- 

 sibly as the 500-feet contour line; but data are absolutely lacking for 

 the definition of its eastern boundary in Arkansas. We know that on 

 the opposite shore of the Mississippi there is no trace of Ozarkian 

 forms. Possibly the upland region of northwestern Louisiana should 

 be added. 



On the northwest, north, and northeast of the Ozark area the wide- 

 spread Carolinian species rule; on the southeast and south the 

 Austroriparian, and on the southwest the uttermost waves of Lower 

 Sonoran life ripple against the rising Ozark mass. The several elements 

 of the fauna are here listed. 



1. Species and subspecies confined to the Ozark fauna: 



Polygyra dorfeuilliana? Polygyra j. deltoidea. 

 d. sampsoni. j. simpsoni. 



d. percostata. labrosa. 



d. perstriata. fraterna imperforata. 



jacksoni. pilshryi. 



* Dr. D. S. Jordan writes: "Streams of the Ozark Mountains similar in char- 

 acter to the rivers of East Tennessee have an essentially similar fish fauna, 

 although between the Ozarks and the Cumberland range lies an area of lowland 

 bayous into which such fishes are never known to penetrate." (Science Sketches). 

 He suggests that the time of mingUng across the lowlands may have been when 

 the intervening region had a colder climate. 



" This species spreads southward as far as Galveston, etc., but it is listed here 

 because it is an abundant Ozarkian form, and has three races confined to that 



