UPPER CARBONIFEROUS 135 



fauna. According to this interpretation, the oldest of the western 

 faunas, which, as already noted, presents a closer resemblance to 

 the characteristic Pennsylvanian fauna than any other, would corre- 

 late with all of the eastern section to the top of the Kansas Permian. 

 Its failure in the strata which it occupies to measure up to the thick- 

 ness of the Mississippi Valley section, and the absence from it of some 

 of the modifications found there, would be ascribed to pre-Hueconian 

 erosion. After this episode there was, it might be claimed, a faunal 

 change represented in the Hueconian fauna of the West and in Mr. 

 Beede's red beds fauna of Oklahoma, this in turn being succeeded by 

 the Guadalupian fauna. 



Though keeping this interpretation of the facts well in mind, I am 

 at present adopting the more conservative hypothesis — that the top of 

 the Kansas Permian may be as high as the base of the Guadalupian; 

 but that no part of the latter correlates with any part of the inverte- 

 brate-bearing beds of Kansas.^ From this it would follow that if the 

 Guadalupian is equivalent to the Russian Permian then the Kansas 

 Permian is distinctly older, possibly Artinskian, possibly Gschelian. 

 If, on the other hand, the Kansas Permian is really equivalent to that 

 of Russia, the Guadalupian would appear to be a distinct and 

 faunally well characterized series younger than the Permian. 



It is well in considering the use of the word Permian for North 

 American strata to discriminate Permian time, Permian conditions, 

 and Permian faunas. Permian conditions, or conditions such as were 

 prevalent in Russia during Permian time, might recur more than once. 

 Indeed, it is safe to say that most conditions are repeated in one area 

 or another many times during geologic history. Permian conditions 

 would give character to the sediments and to the faunas of Permian 

 time. But, while the same peculiarities of sedimentation would 

 presumably be manifested at every recurrence of Permian conditions, 

 the character of the fauna would be partially determined by another 

 factor, the biologic factor. It is conceivable, or even probable, that 

 similar conditions acting upon two unlike faunas might produce 

 rather similar results. The resulting faunas might be less diverse than 

 the original ones. This is perhaps particularly true of conditions 

 such as appear to have prevailed in the typical Permian, conditions 



I By this expression I mean to include the Marion and subjacent formations. 



