334 C. R. KEYES 



In the Russian district one finds it difficult to imagine that he is 

 not wandering through some part of Kansas. Only the presence 

 of the Russian peasant, or sudden contact with a village of the 

 steppes dispels the illusion. In the Upper Paleozoic the aspects 

 of the limestones and shales, their succession and expression 

 are the same on the banks of the Volga or Kama as they are in 

 the bluffs of the Missouri or Kansas rivers. 



The original Permian strata are indistinguishable, lithologi- 

 cally, from the so-called Permian of Kansas. In both there are 

 the same gray and variegated sandy shales and marls, passing 

 locally into sandstones, that are often copper-bearing. Occasion- 

 ally there are present thin bands and beds of buff earthy lime- 

 stone. Gypsum is abundantly developed in beds and interspersed 

 everywhere through the rocks. Saline shales are of not infre- 

 quent occurrence. On both continents all these pass upward 

 into "Red Beds," that are almost destitute of fossils. Whether 

 the last mentioned strata are Permian or Triassic is still, in both 

 countries, an open question. 



Range of faunas. — The succession of faunas appears to be 

 essentially the same in the Russian Carboniferous and Permian 

 as in the Mississippi valley. The composition of each of the 

 faunas is also strikingly comparable. The most noteworthy 

 feature of the organic remains, viewed as a whole, is the gradual 

 replacement of a purely marine type by a shore and brackish 

 water phase, as the change from open sea to closed water con- 

 ditions took place, and finally to those in which life could not 

 exist. 



The most prominent characteristic of the biotic change from 

 a Carboniferous phase to a Permian one seems to be the replace- 

 ment of a predominantly brachiopod fauna by one in which 

 lamellibranchs formed the preponderant element. This change 

 has not, however, the deep significance usually attached to it. 

 There are many other factors- that appear to be largely or 

 entirely overlooked. Faunal considerations should dwell more 

 particularly on some of these other features, rather than upon a 

 detailed tabulation of specific sequence. 



