EASTMAN: CARBONIFEROUS FISHES 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 Measures, 
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 ** Red Beds” or Cimarron series, which ex- 
hibit a thickness further southward 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 the 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. The demarca- 
tion between the two systems is drawn by Frech? 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, 
an arrangement in which a number of writers have concurred. 
Regarding the transitional faunal characters, it is remarked 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 the Upper Palaeozoic Formations of Kansas. Journ. 
Geol., Vol. X., 1902, p. 711. 
3 Journ. Geol., Vol. VII., 1899, p. 354, et seq. 
4 Tbid., p. 360. 
