8 NEW REPTILES AND STEGOCEPHALIANS FROM 



lenses and intercalated beds of small extent. Invertebrate fossils are few, limited 

 to Unios, which are generally so poorly preserved as to be indeterminate specific- 

 ally ; frequently there is an abundance of fossil wood in the form of larger or smaller 

 fragments, but none has been determined. An attempt to determine the wood 

 revealed that it was badly rotted before fossilization and so deeply impregnated 

 with gypsum as to destroy the cell structure. Knowlton's catalogue of the Meso- 

 zoic and Cenozoic plants of North America mentions no Triassic plants from Texas, 

 and those listed from New Mexico are from the central and southern portions. 

 The age of the beds must be determined by the vertebrate fossils, and these indicate 

 an Upper Triassic stage, approximately equivalent to the Keuper of Europe. 



On the borders of the Staked Plains, as in the other regions of the United 

 States where the Triassic is exposed, there seems to be no possibility of determining 

 the boundary between the Permo-Carboniferous beds and the Triassic. The Red 

 Beds are apparently continuous across the interval, and the connecting beds are, so 

 far as known, entirely devoid of any evidence of life. It is in this connecting series 

 of beds, representing the period of the great development of reptilian life in the 

 late Permo-Carboniferous and the early Triassic in South Africa, that some repre- 

 sentation of that life should appear if it were present in North America. Because 

 of this fact the transition beds have been repeatedly searched with the greatest 

 care, but as yet nothing has been found. The only remains that suggest the pres- 

 ence of anything like the South African forms in North America are the prob- 

 lematical fossil found in West Virginia/ 200 feet below the base of the Pittsburgh 

 coal bed and the base of the Monongahela Series, in Braxton County, West Vir- 

 ginia, named Pareiasaurus(?} henningi by I. C. White, and the forms described 

 by Williston, from a few poorly preserved bones, as Eubrachiosamus and Brachy- 

 brachium, from the Popo Agie beds near Landor, Wyoming. The first of these 

 Williston 2 regarded as belonging near to Tapinocephalus or Phocosaurus, and Dr. 

 Broom, in conversation with the author, stated his opinion that it was Deino- 

 cephalian in its affinities. Here, also, should be mentioned the humerus, described 

 by Lucas as Placerias hesternus, from the Triassic near Tanner's Crossing, Little 

 Colorado River, Arizona. 3 These remains are far too little known to permit of 

 any conclusion being drawn from them, and they do not occur in the transition 

 beds, but below and above them. 



The Triassic beds of the borders of the Staked Plains have been divided by 

 Drake 4 into three parts, and his divisions are recognizable in a broad way, but 

 rarely can any definite boundaries be assigned to the divisions, nor can the pro- 

 visional separation made in one place be carried satisfactorily for any distance. 

 Drake described his three divisions as follows: 



1 Case, E. C., Notes on the Possible Evidence of a Pareiasaur-like Reptile in the Conemaugh Series of West 

 Virginia, West Virginia Geological Survey, Braxton and Clay County Report, p. 803, 1917. 



- Williston, S. W., Notice of Some New Reptiles from the Upper Triassic of Wyoming, Journal of Geology, 

 vol. xii, p. 690, 1904. 



3 Lucas, F. B., Proceedings U. S. National Museum, vol. 27, p. 194, pi. iv, 1004. 



4 Drake, N. F., Stratigraphy of the Triassic Formation of Northwest Texas, Third Annual Report Texas 



Geological Survey, p. 227, 1892. 



