136 GEORGE H. GIRTY 



hostile to marine life, hostile especially to the continuance of specialized 

 types of Hfe, at least of brachiopods. 



In the Kansas section we appear to have a single faunal sequence 

 gradually passing to extinction but undergoing some minor modifica- 

 tions in the process. The upper portion of the sequence is the Kansas 

 Permian. We are told by those who are familiar with both, that 

 Permian conditions are manifested in the so-called Permian sediments 

 of the Mississippi Valley. I believe that there is no strictly Permian 

 fauna in that area. The question at issue is: Do the higher inverte- 

 brate-bearing beds of the Kansas section represent Permian time ? 

 On the assumption that such is the case, a comparison of the evolution 

 of the faunas of the two continents is interesting. Let any one 

 acquainted with our eastern faunas look over Trautschold's mono- 

 graph on the Moscovian fauna and he would exclaim at once, "This 

 is our Pennsylvanian facies." Let him next examine Tscherny- 

 schew's monograph on the Gschelian brachiopods, and he would 

 find that nothing at all comparable is known among the faunas of 

 eastern North America. He would even find that the few Pennsyl- 

 vanian species which Tschernyschew has recognized among the Gsche- 

 lian brachiopods are wrongly identified. If he furthermore studies 

 the scattered accounts of the Artinskian and Permian faunas I think, 

 too, that he will find less resemblance between them and the Kansas 

 Permian than has often been supposed. 



Apparently there was a basal generalized type of Upper Car- 

 boniferous fauna distributed over both continents without any wide 

 difference of facies — the Moscovian of Russia, the pre-Hueconian of 

 western North America, and the early Pennsylvanian of eastern. 

 Then changes occurred which brought about striking and similar 

 modification in the faunas of western America and Russia, the Gsche- 

 lian of Russia and the Hueconian of western North America. Then 

 again other changes occurred which brought about a third modifica- 

 tion, this time restricted to western America, or, at all events, not 

 developed similarly there and in Russia. Meanwhile the fauna of 

 eastern North America must have remained essentially static until 

 similar conditions, setting in in Perm and in Kansas, eventually 

 extinguished those already moribund faunas, while the intervening 

 faunas, those of western America, remained vigorous and rich. The 



