NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 93 



Gordon " says the Cisco is not the same as the Wichita and speaks of the 

 separation between them. 



David White ^ is convinced from paleobotanical evidence that the Texas 

 beds are Lower Permian. After giving floral lists from Texas, Oklahoma, 

 and Kansas and pointing out their strong Permian content, he says: 



"The very incomplete collections of fossil plants from the Wichita formation 

 in Texas, from its supposedly approximate equivalents in Oklahoma, frcan the Chase 

 and Sumner groups in Kansas, and from the great series of undifferentiated 'Red 

 Beds ' in the Rocky Mountain region of southern Colorado, showed a mixed flora 

 embracing: (i) mainly representatives of the Permian flora of western Europe, 

 and including many types not previously known in North America; (2) a smaller 

 portion peculiar to the Gigantopteris association in south-central and southwestern 

 China; and (3) several types apparently identical with, or very close to, forms 

 hitherto known only in the Permian or the Uralian region. 



"The distribution of the floral elements indicates that the western European, 

 or cosmopolitan, elements of the flora migrated between North America and Europe, 

 presumably by the same general northeastern route as that followed by their Penn- 

 sylvanian predecessors, while the distinctly Chinese types must have come to Texas 

 and Oklahoma by the north Pacific (Alaskan) route, by which the related Uralian 

 forms may also have migrated. Since the land migration of the Chinese types 

 could hardly have been accomplished ivithout the aid of essential continuity of 

 environmental conditions, and since it is probable that the Gigantopteris elements 

 lived under climatic conditions mainly similar in both Texas and China, the conclu- 

 sion appears justified that the climatic province under which they thrived in Asia 

 extended to western North America, and that it included the region of north Pacific 

 migration. The mingling of western European species with Gigantopteris in the 

 southwestern ' Red Beds ' is construed to indicate that this region was probably on 

 the eastern border of the Gigantopteris province." 



Beede says'" "the Permian age of the beds (in Oklahoma) has been pretty 

 well confirmed." 



LIMITING HORIZONS OF THE VERTEBRATE FAUNA. 



The author of this paper has no intention of making any effort to 

 determine exactly the horizon of the vertebrates here called Permo- Carbon- 

 iferous. The exact valuation of these beds must be accomplished by the 

 workers in invertebrate paleontology, aided by detailed comparison of the 

 American vertebrates with those of the rest of the world, which would be 

 quite beyond the limits of this work and must be reserved for future papers. 



Prosser, Beede, Girty, Gould, Schuchert, and others have attempted to 

 determine the horizon of the beds from invertebrate fossils and have not 

 reached concordant results. All that is attempted here is to locate in 

 accepted terms the upper and lower limits of the beds which represent the 

 time of the vertebrate fauna here discussed. For this purpose the lower limit 

 of the Permo-Carboniferous beds is tentatively drawn at the base of the 



• Gordon, with Girty and White, Jour. Geol., vol. xix, No. 2, pp. 119 ,120, 1911. 

 •> White, Proc. U. S. Nat. Mus., vol. 41, p. 513, 1912. 

 "Beede, Oklahoma Geological Survey, Bull. 21, p. 37, 19 14. 



