M-\V KK1TILKS AM) STEGOCEPHALIANS FROM THE UPPER TRIASSIC 



OF WESTERN TEXAS. 



BY E. C. CASE. 



INTRODUCTION. 



By aid of grants from the Carnegie Institution of Washington, the author 

 has been for a number of years continuously at work upon the investigation of 

 the vertebrate fauna of the Permo-Carboniferous beds of North America. The 

 sudden and complete disappearance of this fauna (followed, after an interval 

 represented by barren beds, by a highly specialized Upper Triassic fauna) has 

 always been a tantalizing problem the more so as the barren beds between the 

 two widely different faunae are practically the same, in all the implications as to 

 climate, mode of deposition, and terrestrial conditions, as the fossiliferous beds 

 above and below. 



The interval of time represented by the barren beds is just the interval in 

 which was developed the wonderful Permian and Triassic reptilian life of South 

 Africa, Russia, and western Europe. A few very uncertain remains, briefly dis- 

 cussed in the section of this paper dealing with the Upper Triassic beds of western 

 Texas, suggest the possibility that something of the Lower Triassic life of the 

 Eastern Hemisphere reached North America. For these reasons the barren beds 

 have been followed and searched with extreme care wherever they occur, but so 

 far no trace of vertebrate life has been found in them. While engaged in such a 

 search, the author learned of a small area in Crosby County, Texas, which has 

 yielded a considerable amount of Upper Triassic vertebrate material, most of 

 which is new. The present paper contains descriptions of this new and interesting 

 fauna. 



The author takes this opportunity to thank the Carnegie Institution of Wash- 

 ington and its officers for the continued support which has made the work possible. 

 Also, he wishes to acknowledge his obligation to Mr. Clifford Jones, manager of 

 the Spur Farm Lands Company, and the other officers of the Swenson properties, 

 for permission to go upon the lands under their control and for many acts of kind- 

 ness and courtesy which rendered the task of collection much easier and con- 

 tributed largely to the success of the work. 



THE UPPER TRIASSIC BEDS OF THE BORDERS OF THE 



STAKED PLAINS. 



The Upper Triassic beds exposed on the borders of the Staked Plains in 

 Texas and New Mexico present the same puzzling complex of terrestrial and 

 fresh-water deposits that they do wherever they appear in the other Plains and 

 Rocky Mountain States. No definite determination of continuous horizons is 

 possible, as the sequence alters rapidly within a short distance and there are many 



