ART. 18 AGE OF NORTH AMERICAN TEIASSIC BEDS VON HUENE 3 



gistorhinus, Aco?npsosaurus, and Metoposaurus fraasi — lived long 

 before the close of the Triassic period and that there was a later 

 vertebrate fauna. 



On several occasions the writer has shown that some of the 

 Parasuchians found in Wyoming and Arizona are of a very primi- 

 tive type {Palaeorhiiius, Angistorhinus) , others lessso,a.sMacIiaero- 

 prosopus and Heterodontosuchius. It seems questionable whether 

 the European genus Phytosaurus does not also occur here. The 

 Labyrinthodonts all belong to the family Metoposauridae, which in 

 Europe is of lower Keuper age. Acompsosmirus, as shown else- 

 where,^ is probably nearly related to the primitive parasuchian 

 Desmatosuchus, and is not a Pelyeosaurian. 



At Morrison, near Denver, Colo., the Red Beds fall into three 

 divisions. At the base is the coarse-grained Fountain formation, 

 to which belong the fantastic, nearly perpendicular pillars of red 

 sandstone in the " Garden of the Gods," near Colorado Springs, and 

 in " Rocksbury Park," near Morrison ; in the middle is the Lyons 

 formation, to which belong the white quartzitic sandstones (" Creamy 

 sandstones"), which are clearly visible in the landscape; and the 

 uppermost beds, the Lykins formation, consisting of soft reddish 

 and whitish beds, of which Williston's Hallopus teds near Canyon 

 City form the upper part.^ These directly underlie the Upper 

 Jurassic Morrison beds. The Fountain formation is now accepted as 

 being good Pennsylvanian ; ^° Lyons sandstone, as Pennsylvanian; 

 lower Lykins, as Permian; upper Lykins, as Triassic, and more or 

 iess an equivalent of the Chugwater formation of Wyoming. 



Farther to the northwest in the region of Lander, Wyo., below the 

 Oxfordian marine Jurassic Sundance beds (with Belemnites^ 

 Gryphaea^ and Baptanodon)^ are red beds, usually designated the 

 Chugwater formation, nearly 300 meters in thickness, in whose 

 upper 70 meters, the '" Popo Agie beds," a number of vertebrates have 

 been found, and more recently some unios and plants described by 

 E. AV. Berry.^^ The Popo Agie beds are apparently equivalent to 

 Knight's Jelm formation^- of southern Wyoming and are clearly 

 separated from the overlying marine Jurassic (Sundance) beds and 

 the underlying red beds. From a paleontological standpoint, the 

 writer is forced to consider the fauna of the Lander as being of the 

 same age as the lower fauna of the Colorado Plateau. Both must 

 be Middle Triassic. From the literature and from personal observa- 

 tion, it is thought that the geological data are not adverse to this 

 conclusion, Parasuchians such as Palaeorhinus and Angistorkinus, 



8 Gondwana — Reptilien in Siidamerika. Pal. Hung. 1926 



•Williston, S. W., Journ. Geology, vol. 13, 190.5, pp. 338—350. 



1" J. Hendei-son, Colorado Geol. Surv., Bull. 17, 1920. 



" Journal of Geology, vol. 22, 1924, pp. 488-497. 



" Knight, S. H., Geol. Soc. America, Bull., vol. 28, p. 168, 1917. 



