INTERPRETATION OF ENVIRONMENTAL CONDITIONS 193 



The occurrence of Permo-Carboniferous reptiles and amphibians as low as 

 middle Conemaugh is no longer a puzzle; the animals appeared with the 

 environment and migrated with it; they are strictly within the limits of 

 their proper environment wherever they occur. 



The sequence in the evidence for the progressive advance of the climatic 

 change which induced the deposition of red beds is broken in two places — 

 at the Cincinnati anticline and at the elevation in Missouri. All efforts to 

 trace the change around these elevations have been only partially successful. 

 The breaks are in part due to the effects of erosion removing all trace of 

 Permo-Carboniferous deposition and in part to the fact that these areas 

 were above the plane of deposition before the migrating climatic change 

 had reached that far west. 



One apparent conclusion from the premises here stated is that the Permo- 

 Carboniferous vertebrate fauna originated in the eastern part of North 

 America and migrated westward. This the author is not yet entirely 

 ready to accept, but he is strongly impelled toward the conclusion by the 

 facts that the earliest known reptile, Eosauravus, was discovered in the 

 Allegheny series, at Linton, Ohio; that typical Permo-Carboniferous verte- 

 brates appeared in middle Conemaugh time in Pennsylvania and West 

 Virginia; and also that typical pelycosaurs occur in the red beds of Prince 

 Edward Island at a stratigraphic level much lower than those of Oklahoma 

 and Texas. 



B. INTERPRETATION OF CONDITIONS IN ALLEGHENY AND 

 LOWER CONEMAUGH TIME. 



As already mentioned, the conditions during pre-Conemaugh Penn- 

 sylvanian time were radically different from those in the late Paleozoic. 

 The clastic sediments, coal beds, mode of deposition, etc., are all those of 

 an inclosed basin of singularly monotonous character. Perhaps the best 

 picture that has been given of the various minor basins of the Eastern 

 Province is that by David White :^ 



"Terrestrial Conditions. 

 "Base-Level Basins. 



"The examination of the strata intervening between the coal beds in the great 

 coal fields of the earth and the inspection of the coal show conclusively that 

 nearly everywhere the vegetal matter was deposited and transformed to peat 

 beneath a water surface. Furthermore, in the great majority of the basins, 

 including nearly all the great coal areas,^ the coal (peat) was laid down not far 

 from tide-level, marine beds being intercalated at various horizons in the coal- 

 bearing series of rocks, and not rarely in the beds immediately overlying the 

 coal itself. In certain basins brackish-water mollusks are found in many of the 



* White, David, The Origin of Coal, Bureau of Mines Bull. 38, pp. 52-60, 1913. 



' The very extensive basins of the Fort Union coal in the northern Rocky Mountains region 



are regarded as fresh-water basins, 

 14 



