CORRELATIONS 679 



species, together with immigrants from other regions. 15 The conditions 

 responsible for this rapid development accomplished the rapid elimina- 

 tion of the Pennsylvanian forms. 



In the light of the evidence furnished by the fossil plants, namely, that 

 all the typical Pennsylvanian species had been removed from the Onaga 

 flora, leaving only those that persist into the Permian, and the presence 

 of a well developed Permian flora in the Wreford limestone, it would 

 seem that the Permian flora first appeared in an intermediate formation, 

 more likely quite as near to the lower as to the upper horizon. 



Similarly, faunal elements begin to appear in the Elmdale formation, 

 which persist into the Permian, and Schwagerina and its accompanying 

 fauna appear in the Neva limestone. Hence the line between the Penn- 

 sylvanian and Permian periods is placed at the base of the Neva limestone. 



From the review of the fauna and the flora characterizing the Western 

 and Eastern sections, it is found that the correlations based on the two 

 types of evidence is not seriously discordant. Indeed, it is nearly as har- 

 monious as one might expect for correlations based on marine inverte- 

 brates and on land plants, and there appears to be little reason to ques- 

 tion these correlations, though the correlation based on the fossil plants 

 would place the Conemaugh formation lower in the Kansas section than 

 that based on the invertebrates. For present purposes, the difference is 

 negligible. 



SUCCESSION OF THE VERTEBRATES AND CORRELATION OF THEIR 



HORIZONS 



With this history of the range and distribution of the invertebrates and 

 plants of the latest Pennsylvanian and basal Permian beds in mind, it is 

 interesting to turn to the analysis of the occurrence of the vertebrates 

 which existed during the same periods of time. The following table shows 

 the distribution of the vertebrates in the Appalachian and Western sec- 

 tion : 16 



D. White : Jour. Geol., vol. xvii, 1909, p. 335. 



Case : Carnegie Institution of Washington, Publication No. 107. 1915. 



Moodie : Carnegie Institution of Washington, Publication No. 23S, 1910. 



