EASTMAN: CARBONIFEUOUS FISIIE.S FROM THE CENTRAL WEST. 165 



stitute a distinct terrane, — often referred to as the Permo-Carboniferous, 

 — the majority of its species being common to the Upper Coal Measm-es, 

 and perhaps one-half of the species occurring in the succeeding 300 or 400 

 feet (Sumner stage of Cragin) being also common to them. But in the 

 upper terrane, the so-called " Rod Beds " or Cimarron series, which ex- 

 hibit a thickness further soutliward of from 1000 to perhaps 2200 feet, 

 no fossils have been found which are at all closely related to those of 

 the Coal Measures, and writers are pretty generally agreed in cor- 

 relating this series with tlie Upper Permian (Neo-Dyas) of Europe. 



In the same way there appears to be good reason for believing that 

 the lower part of the Big Blue series (Chase and Neosho strata) corre- 

 spond to the Artinsk stage, which is the oldest Permian of Russia. 

 Owing to the absence of Cephalopods, however, and general transitional 

 character of the Neosho, no distinct line of separation between the 

 Lower Permian and Carboniferous can be said to exist. Tlie demarca- 

 tion between the two systems is drawn by Freeh ^ at the base of the 

 Chase stage, and this limit for the Lower Permian is also accepted by 

 Prosser,^ who places the Neosho member at the summit of the Mis- 

 sourian. In Prosser's original description of these formations, however, 

 the line of separation between the Upper Coal Measures and Permian 

 was doubtfully drawn between the Cottonwood and Neosho formations, 

 au arrangement in which a number of writers have concurred. 



Regarding the transitional faunal characters, it is reraarketl by Keyes* 

 that " the most noteworthy feature of the organic remains, viewed as a 

 whole, is the gradual replacement of a purely marine type by a shore 

 and brackish water phase, as the change from open sea to closed water 

 conditions took place, and finally to those in which life could not exist. 

 ... In this region as in Russia, the gradual replacement of a brachio- 

 podous fauna by a Permian lamellibranch fauna follows the local change 

 of open to closed sea conditions. The Permian element of these forms 

 was merely a shallow water facies of the more typical Carboniferous 

 fauna." 



In Nebraska the so-called Permo-Carboniferous (Chase and Neosho) 

 strata form the northern continuation of the Kansas beds, and agree 

 with them in all essential characters. The area is described by Knight * 



1 Lethaea Palaeozoica, Vol. II., 1899, p. 378. 



2 Revised Classification of tlie Upper Palaeozoic Formations of Kansas. Journ. 

 Geol., Vol. X., 1902, p. 711. 



3 Journ. Geol., Vol. VII., 1899, p. 354, et seq. 



4 Ibid., p. 860. 



