THE UPPER TRIASSIC OF WESTERN TEXAS. 11 



of it is grassed, so the exposures are limited in extent; but they are uniformly of 

 red clay and red sandy shale, with occasional layers of more or less heavy brown 

 sandstone and thin beds of grit or conglomerate. Throughout this area fragmen- 

 tary remains of Phytosaurs and Stegocephalians occur in small quantity. The 

 rolling country continues westward to and beyond Tucumcari in Quay County. 

 About 5 miles west of San Jon, in Quay County, there is an area of river deposits 

 with beds of conglomerate, heavy sandstone, loose gravel, and clay; the change in 

 the character of the beds is reflected in the nature of the surface, for the region 

 is locally known as the Bad Lands. In this limited area remains of Phytosaurs 

 and Stegocephalians occur, similar to those found in Crosby County, Texas, but 

 in far smaller number and in a poorly preserved condition. 1 Beyond San Jon the 

 surface of the country again becomes more regular, reflecting the more uniform 

 character of the beds beneath. 



At Mount Tucumcari and along the west front of the Plains there is, in gen- 

 eral, a more uniform sequence of the beds than on the east side. A heavy mass of 

 red clay and red sandy shales is overlain by a second heavy bed of sandstone which 

 may be white, as directly west of Montoya, or brownish farther to the west and 

 south, typically exposed at Cuervo, in Guadalupe County. These dominant heavy 

 beds of clay and sandstone are frequently interrupted by locally developed beds 

 of lighter-colored clays and sands, white, yellow, or blue, in which poorly preserved 

 fragments of bones occur in limited amount. The same character of the beds is 

 found as far west as Santa Rosa, in Guadalupe County, and as far south as beyond 

 Roswell. East of Roswell the red beds contain much more gypsum than those 

 farther north, and no remains of vertebrates have been found in them. 



A reconnaissance from Montoya westward through Isidor, Buxton, and Cabre 

 Springs and up the Conchas Canyon to Las Vegas showed that the beds retained 

 a similar character until they disappeared beneath the Cretaceous. It is evident 

 that the great bulk of the Triassic beds revealed on the borders of the Staked Plains 

 and in eastern and central New Mexico were deposited under conditions unfavorable 

 to the preservation of vertebrate fossils. The more uniformly deposited beds of 

 clay and shale were apparently laid down in deep water or in water far from the 

 shores; it is only in the disturbed beds, which bear evidence of having been de- 

 posited by great flood washes, that the remains of animals and plants are found. 

 Such remains are usually badly broken and water- worn ; occasionally good specimens 

 will turn up, as evidenced by the presence of a skull of a Phytosaur preserved in 

 the University of Chicago, which was obtained from the School of Mines at Socorro, 

 New Mexico, and said to come from near Santa Rosa, 2 and from some remains 

 secured by the author near Carthage, Socorro County. It is only in such rare 

 occurrences as the section of some large river flood-plain, such as occurs in eastern 

 Crosby County, Texas, that good material will be found. The rarity of such occur- 

 rences is shown by the experience of the author, who, in four trips in the regions 

 mentioned, has found only the single exposure. 



1 For a more detailed description of the Bad Lands west of San Jon, see an article by the author in the Journal 



of Geology, vol. xn, No. 3, 1914. 



2 Mehl, M. G., A New Phytosaur from the Trias of Arizona, Journal of Geology, vol. xxx, p. 144, 1922. 



