HOMOTAXIAL EQUIVALENTS OF THE PERMIAN 333 



In the consideration of a theme like the present one, it is 

 recognized at the outset, that comparisons of terranes of different 

 geological provinces involves no necessary exact synchrony, 

 except through absolute physical means of correlation. Such a 

 standard, independent of intrinsic features of the terranes them- 

 selves, is not yet formulated for widely separated districts. The 

 shortcomings of the common fossil criteria, in any other than 

 the most general way and in the absence of something better, 

 are well known. Any agreement of biotic features in strati- 

 graphic successions distantly removed from one another are 

 looked upon, so far as indicating simultaneous origin, only as 

 happy accidents. Instead of furnishing proofs of time equiva- 

 lency, it suggests for similar faunas only likeness of conditions, 

 irrespective of time. Such faunal facies are only representative. 

 They are merely homotaxial. 



Any similarity of lithological succession is likewise accidental. 

 The same is manifestly true of any other agreement of intrinsic 

 features. 



Nevertheless, a comparison of general geological sections in 

 provinces so widely separated as the two under consideration, 

 and so wholly distinct from each other in their origin, can be 

 made not only suggestive but very profitable. The same prob- 

 lems for solution arise in both districts. The naturally different 

 manner of treatment is mutually helpful in the solution of the 

 various difficulties that are presented. Misconceptions regard- 

 ing each are dispelled. Greater independence in the considera- 

 tion of succession is established. 



The most remarkable fact connected with the Russian section 

 of the Upper Paleozoic and that of Kansas is that the two should 

 be capable of any comparison at all. While the two differ much 

 in stratigraphic, lithological, and biotic details, in general all 

 three classes of characters present a very similar sequence. 



Litliological features. — In the Russian and American Permian 

 provinces, the field appearance of the rocks is verv strikino-ly 

 alike. This is particularly true of the upper half of the two sec- 

 tions. The general features are lost in the local examinations. 



