NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 73 



1907 Girty reported that the fauna and horizon are those which in the Fortieth 

 Farallel Survey reports are called Permo-Carboniferous, and said: 'It seems prob- 

 able that the fauna will be correlated with the Permian of the Grand Canyon 

 section. ■' 



Girty later referred these fossils to the Triassic and "almost certainly 

 equivalent to the Triassic of Idaho." His latest statement, in 1910,- seems 

 to indicate his belief that there are deposits of Permian or Permo-Carbonif- 

 erous age in this region. He says: 



"In notable contrast to the Weber formation, the beds above the Park City 

 formation show striking persistence in their main lithological and paleontological 

 characters. These are the ' Permo-Carboniferous ' beds of the King survey and were 

 divided by Boutwell in the Park City district into the Woodside, Thaynes, and 

 Ankareh formations. It seems all but certain that the 'Permian' of Walcott's sec- 

 tion in the Kanab Canyon, in southern Utah; the 'Permo-Carboniferous' of the 

 Wasatch Mountains in northern Utah; and, in part, the 'lower Triassic' of south- 

 eastern Idaho are one and the same series. The Woodside, Thaynes, and Ankareh 

 do not, perhaps, maintain precise boundaries throughout all this territory, and in 

 Idaho the first occurrence of Triassic ammonites {Meekoceras beds) is convention- 

 ally taken as the base of the Thaynes. 



"The Triassic age of at least the major portion of the 'Permo-Carboniferous' 

 (Thaynes and Ankareh) seems to be shown by fairly satisfactory evidence— the 

 presence of an extensive ammonite fauna of Triassic type and the practical absence 

 of any distinctive Carboniferous forms. In advance of a detailed study of these 

 faimas, however, it may be pointed out that above the Meekoceras beds there are 

 zones which contain great numbers of Rhynchonella closely related to the Carbonif- 

 erous Pugnax Utah and many specimens of apparently true Myalina, not unlike 

 Carboniferous species. 



" It is much less certain that the Woodside formation is not Paleozoic (Permian ?). 

 A preHminary study of the Woodside shows that, except that it has yielded no am- 

 monitic forms, it does not differ materially from the fauna of the Thaynes and 

 presents a strong contrast to the Carboniferous fauna of the Park City. Lithologi- 

 cally also there is a well-marked division between the Woodside and the Park City 

 formation, and no lithological boundary can be traced between the Woodside and 

 the Thaynes. That the Woodside, Thaynes, and Ankareh form a natural group is 

 indicated by the classification of the rocks adopted by most geologists. If the 

 Thaynes is Mesozoic, the obvious line between the Mesozoic and the Paleozoic would 

 seem to be the line between the Park City and the Woodside. If, then, as may be 

 tentatively concluded, the Woodside does not represent the Permian, the natural 

 question to follow is: Does the Park City formation belong in the Permian? A 

 decisive judgment on this point should wait upon a careful study of the faunas 

 obtained from other members of the Park City beds, as well as upon a study of other 

 related faunas less certainly appearing at the same horizon. Because of the close 

 relationship or identity of many species of these faunas with the Gschelian faunas 

 of Russia, I am provisionally holding that the Park City formation is older than the 

 Permian. 



"Any one at all familiar with the Carboniferous faunas of the Mississippi Valley 

 will at once recognize that the forms found in the phosphate beds, individually as 

 well as collectively, are quite different from the forms found in that area." 



" Girty, Bull. U. S. Geological Survey No. 436, pp. 7-10, 1910. 



