NORTH AMERICA AND THEIR VERTEBRATE FAUNA. 



91 



The two provinces of Red Beds as outlined in this paper can only be con- 

 sidered as great flood-plains or deltas (in Barrel's broad interpretation of 

 that word). 



East of the Permian limestones of Texas, Oklahoma, Kansas, and Ne- 

 braska the surface of North America was probably very largely out of water; 

 the few evidences of river channels, local pools, etc., are sufficiently meager, 

 but by their very meagerness indicate the large extent of land surface. Had 

 there been deposits of any extent from marine or fresh waters some traces 

 would have tmdoubtedly remained to us, for the eastern half of the Missis- 

 sippi Valley has been a region of comparatively slight degradation since the 

 close of the Paleozoic. 



