HOMOTAXIAL EQUIVALENTS OF THE PERMIAN 339 



been called the Mississippian series. In its broadest sense the 

 so-called Lower, or Productive Coal Measures finds satisfactory 

 expression in the Des Moines series. For the " Upper Coal 

 Measures " nearly to the usually selected horizon for the base 

 of the Permo-Carboniferous, Missourian has been suggested as a 

 serial name. 



The uppermost division of the Paleozoic of the region, the 

 part widely designated as the " Red Beds," has received the 

 title of Cimarron series. It appears to form a tolerabty compact 

 sequence, though there is still some dispute as to its exact 

 geological age. Between the Cimarron series and the Missourian 

 series are two other terranes that are well defined. One is com- 

 posed of the Chase and Marion of Prosser, in part, and the 

 other of the Wabaunsee, Cottonwood, and Neosho. 



Should some such subdivision of the Upper Paleozoic be 

 found applicable over the larger portion of the Mississippi basin, 

 as now seems likely, the use of Permian and Permo-Carboniferous 

 will be rapidly discontinued, or will be invoked only in historical 

 reference. 



RELATIONS OF " UPPER PERMIAN " TO TRIASSIC 



There is little satisfactory data upon which to correlate the 

 beds called Triassic in eastern United States with other regions. 

 The determinations appear to have been largely made upon litho- 

 logical grounds and plant remains. There is no real physical 

 relation between the Triassic, or Newark in the main, of the 

 Atlantic border, and the Triassic of the region lying to the east 

 of the Rocky Mountains. 



The " Red Beds " of Kansas and Texas are thought by some 

 writers to be Triassic in age ; by others Permian. In the almost 

 total absence of fossils in these beds, the lithological characters 

 and general red coloration have been resorted to as criteria. Of 

 late the question has been taken up anew. Prosser has been led 

 to believe that the greater part of the Kansas " Red Beds " are 

 Triassic. Williston, from even more reliable data, is inclined to 

 regard the lower part at least as Paleozoic. 



