126 GEORGE H. GIRTY 



If such citations are included as species identified, 48 species of the 

 fauna are identified and 27 are unidentified. Of the 48 species 

 identified, 37 are known to occur in the Pennsylvanian rocks of 

 the Mississippi Valley. Most of them are cited by Dr. Beede in 

 his table showing the Pennsylvanian faunas of Kansas. The large 

 percentage of indeterminata introduces a considerable possibility 

 of error in the inference that 75 per cent of the fauna of the Wichita 

 formation consists of well-known Pennsylvanian types, but it is 

 undoubtedly true that in the main this fauna has a Pennsylvanian 

 facies. One or two new forms at present excluded from the identi- 

 fied species would somewhat decrease this percentage. On the 

 other hand, of the 25 per cent which is not known to occur in the 

 Pennsylvanian of the Mississippi Valley, relatively few species are 

 characteristic of the Permian of that area; still fewer, if any, 

 are characteristic of the Permian of Europe. Some of them occur 

 in western faunas, probably contemporaneous with the eastern 

 Pennsylvanian. Bellerophon subpapillosus is one of these. Twenty- 

 five in a hundred, therefore, far overstates the percentage of char- 

 acteristic Permian species. Such percentage, however, might be 

 considerably increased by the inclusion of certain species known 

 to occur in the Wichita formation but not represented in the Survey 

 collections. I refer especially to the Ammonite forms described 

 by C. A. White from the Military Crossing of the Wichita. These 

 are by all means the most diagnostic Permian types of the fauna. 

 How little characteristic of it they really are, however, is shown 

 by the fact that later collections made at the same place fail to 

 contain them, although a special search was made to secure addi- 

 tional representatives. 



Mr. White finds that about 50 per cent of the Wichita flora 

 consists of species characteristic of the Permian, while most of 

 the remainder are known to occur in rocks regarded as of Permian 

 age. If we omit the fauna of the Kansas Permian, to include 

 which would be a sort of circulus vitiosus, no condition comparable 

 to this has been demonstrated by the invertebrate fossils and, in 

 so far as I have seen the evidence, no such condition exists. I am, 

 therefore, accepting the Permian age of the Kansas and Texas 

 beds, but at present strictly on the paleobotanic evidence. 



