NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 7 



uncertain relationship" surrounding the Wichita Mountains and occupying 

 all of Tillman County and parts of Comanche, Jackson, Greer, Kiowa, Caddo, 

 Washita, and Cotton Counties. Vertebrates have been found only in the 

 Enid formation, the portion of the Red Beds to the east, reckoned as equiva- 

 lent to the Wichita, not having yielded vertebrates, and the Blaine and 

 Woodward being, so far as known, equally barren. All the well-known 

 fossils from Oklahoma came from Grant, Kay, Noble, Garfield, and Logan 

 Counties, but a few have been found in Tillman and Comanche Counties. 

 Because the Texas beds have been most thoroughly explored and have 

 yielded the largest number of vertebrate fossils and are most completely 

 exposed by the erosion of the surface, they are here taken as a typical region 

 and will be described with considerable detail; other regions mentioned 

 will be compared with these beds as the standard. 



FORMATION NAMES. 



After reviewing the very considerable literature, it seems best to the 

 author to retain the names Wichita, Clear Fork, and Double Mountain, 

 proposed by Cummins. Gordon "" retains the name Wichita "for the for- 

 mation overlying the Cisco," with a revised description, and abandons the 

 name Albany. He describes the upper portion of the beds as "undifferen- 

 tiated Clear Fork and Double Mountain." To one who, in searching for 

 fossils, confines his attention to limited areas and passes slowly over the 

 beds intent on details, and is frequently occupied in an attempt to follow 

 a single layer, these beds present a hopeless tangle. The author has else- 

 where expressed his inability to distinguish a clear dividing-line between the 

 Wichita and the Clear Fork, but now believes that it may be recognized at 

 the first appearance of beds of limestone, although Gordon includes some of 

 these in the Wichita series. To the stratigrapher who passes over the country 

 more rapidly, scanning large areas and correlating, by resemblances based on 

 the average character, a more satisfactory separation may be possible. 



Gordon's latest statement concerning the usage of names is as follows: ^ 



"Although much has been written concerning the beds between the Cisco 

 formation and the Triassic beds which underlie the 'Staked Plains,' much detailed 

 stratigraphic work remains to be done in this region before authoritative statements 

 can be made about the classification of these beds. On the evidence of fossil remains, 

 found chiefly in the lower beds in Baylor and Archer Counties, these strata are 

 now assigned by most geologists to the Permian. These rocks, as they exist in 

 the Wichita region, were subdivided by Cummins into the Wichita, Clear Fork, 

 and Double Mountain formations. The lowest formation, the Wichita, consisting 

 mainly of red clays and sandstones, is seemingly a near-shore or delta deposit, 

 and in it are found the remains of reptiles and plants of Permian age. Interstratified 

 with the clays and sandstones in the upper part of the formation are beds of lime- 

 stone containing marine invertebrates, of which a large proportion are Pennsyl- 



* Gordon, Jour. Geol., vol. 19, p. 125, igii. 



i" Gordon, U. S. Geological Survey, Water Supply and Irrigation Paper No. 317, pp. 21-22, 1913. 



