154: C. Schuchert — Russian Carboniferous and Permian. 



events in a given area; but when it comes to correlating these 

 local sections with those of other continents, there is great 

 diversity of interpretation relative to the values to be placed on 

 the varying faunas. This lack of harmony is primarily due to 

 the absence of a continuous faunal sequence in any one region. 

 Further, some paleontologists draw their species finely, others 

 broadly ; and as all the Carboniferous faunas have a general 

 facies in common, far more decided than that of any other 

 Paleozoic system, and finally, as many of the groups of brachio- 

 pods, the prevailing fossils of the Carboniferous and Permian, 

 have lost their power for rapid or marked progressive evolution, 

 with a decided tendency toward degeneracy, the possibility 

 for wide differences of opinion regarding sequential change in 

 faunas is apparent. Then, too, the centers of radial dispersion 

 of the faunas have not yet been determined, so that no reliable 

 means exists for ascertaining the differences in age of the same 

 or closely related faunas between widely separated areas. How- 

 ever, as the Carboniferous is nearly everywhere characterized 

 by an abundance of fossils, and as there is already an extensive 

 literature on the subject, a final interpretation of the sequence 

 of events, that will carry conviction to all workers, may very 

 soon be looked for. 



2. To the present writer, it is clear that the Permian fauna 

 of the Urals and Timan is not the normal marine one perpetu- 

 ating the Paleozoic sequence in the Mesozoic. (The same is 

 true for Germany and England.) Of brachiopods are missing 

 here the plicate and other types of terebratuloids other than 

 Dielasma and everything from which the rhynchonelloids can 

 be developed, spire-bearing forms and the strophomenoids of 

 the type of the Lyttoniidse. The same is largely true for the 

 other classes of organisms ; in fact, one can better trace the 

 Triassic faunas of the Alps through the Ural and Timan faunas 

 of a lower horizon, i. e., those of the Schwagerina zone. These 

 facts are admitted by Tschernyschew, but it seems to the re- 

 viewer that he fails to give proper weight to the probability 

 which one almost wishes to state with certainty, that somewhere 

 the Schwagerina fauna or one closely related to it continued 

 to maintain itself, and, further, that in some region far away 

 from the Urals and Timan it will necessarily hold a higher 

 tratigraphic position, although somewhat changed in faunal 

 facies. This center of dispersion was seemingly the Mediter- 

 ranean region ; in fact, it is the belief of the reviewer, derived 

 from a knowledge of the Permian of Sicily and Austria, that 

 this great body of water, Thetys, was the home of the normal 

 marine Carboniferous and Permian faunas of Europe and 

 Asia. From Thetys, the faunas spread to the north into the 

 epicontinental seas' of Germany and European Eussia, but in 



