J. YV. BEEDE BEDS OF APPALACHIAN AND WESTERN SECTIONS 



The fact that the earlier vertebrates are now known only from the 

 eastern region and the highly specialized forms are confined to the west- 

 ern deposits demands consideration, as does tentative suggestions thrown 

 out by Case, 17 to account for this distribution. 



REVIEW OF CONDITIONS VERSUS TIME HYPOTHESIS 



The main idea in Case's suggestion is that the Appalachian region be- 

 gan to emerge early in Pennsylvanian, or even Mississippian, time, and 

 that the process was continuous until the whole of the eastern and central 

 United States became a land area, at the close of the "Permo-Carbon- 

 iferous." It is also postulated that a local climatic change occurred at 

 the inception of this movement and continued to its consummation, 

 finally migrating westward with the emerging land. 



He distinctly states this hypothesis in an article entitled "Permo-Car- 

 boniferous Conditions versus Permo-Carboniferous Time." 1S In another 

 place he described at length the supposed climatic and physical condi- 

 tions, the faunas, and their vertical range and geographic distribution. 19 



Regarding the data on which the hypothesis is based, he states : 20 



"The lower limit of the fauna is confessedly vague and shadowy, passing 

 far down into the Pennsylvanian. The Pennsylvanian amphibians described 

 by Moodie in numerous papers are so close to those occurring in association 

 with the Permo-Carboniferous forms from Texas that it is evidently a case of 

 overlapping, and the only recognizable line is that where the first reptile oc- 

 curs. It is. of course, probable that the reptiles occurred at lower horizons. 

 In 1910 Moodie found a form near Cricotus in the Mazon Creek shales. These 

 shales occur near the base of the Allegheny (or top of the Pottsville). David 

 White regards them as the equivalent of coal No. 2 of Illinois (Morris and 

 Braidwood coals of the Clarion). They are regarded by him as having close 

 relationship with the Cherokee of Henrietta County, Missouri, at the base of 

 the Allegheny." 



"The Linton coal, from which comes Eosauravus copei Williston, . 

 belongs to the Upper Freeport coal (coal No. 6.), and is referred by Prosser tc 

 a position near the top of the Allegheny. . . . Williston and Moodie have 

 described the genus Eosauravus, giving figures, and demonstrated its reptilian 

 nature. 



"The earliest amphibians definitely comparable to the Texas fauna are from 

 the Pittsburgh red shale. The Pittsburgh red shale lies 300 feet above the 

 Freeport coal and 695 feet or more below the base of the Dunkard." 



"The exact age of the beds in Illinois (Danville) and Prince Edward Island, 

 in which similar forms occur, is not yet determined." 



17 E. C. Case : Permo-Carboniferous conditions versus Permo-Carboniferous time. Jour. 

 Geol., vol. xxvi, 1918, pp. 500-506. 



18 Jour. Geol., vol. xxvi, 1918, pp. 500-506. 



v -' Carnegie Institution of Washington. Publication 207, PUT). 

 2C Op. cit.. pp. 93-99. 



