HOMOTAXIAL EQUIVALENTS OF THE PERMIAN 33 I 



terrane (CP C ), made up of dolomitic limestones largely, is the 

 basal number of Murchison's original Permian. 



The bottom terranes of the Permian, as now recognized 

 by the members of the Russian geological survey, present a 

 great paucity of fossils. The forms are chiefly lamellibranchs, 

 yet in some layers are fragmentary plants. 



The median part of the Permian carries what has been 

 regarded as the typical German Zechstein fauna. 



About the upper terrane there is much dispute as to age. 

 The Russian geologists are about equally divided. Amalitzky 

 considers it Permian. By others it is regarded as Triassic. 

 Fossils-occur rarely. Those found are chiefly lamellibranchs. 



Base of Murchisori s Permian. — As already noted incidentally, 

 the lower limit of the original Permian, as established by Murchi- 

 son in 1 841, is the bottom of the dolomitic limestone immediately 

 overlying what is called the Artinsk terrane. The geologists 

 who have worked in the region place this line in the middle of 

 the Permo-Carboniferous. The succession of strata and the 

 sequence of faunas are continuous from the Carboniferous to 

 the Permian. The transition is so gradual that it appears 

 impossible to locate a satisfactory line of division between the 

 two. The conditions are identical with those that we have 

 encountered in this country, and, following our example, the 

 Russians have adopted our term — Permo-Carboniferous. 



While the adoption of such a course emphasizes the transi- 

 tionary character of the faunal sequence, it complicates, rather 

 than simplifies, matters. Two important divisional phases are 

 recognized, both of which are as vague and unnatural as the one 

 that this plan aims to obviate. On all other than faunal grounds, 

 Murchison's lower limiting horizon of the Permian is the most 

 satisfactory and perhaps also the most natural. 



COMPARISON OF THE RUSSIA AND MISSISSIPPI VALLEY CARBON- 

 IFEROUS 



Stratigraphic parallelism. — In Russia and in the Mississippi 

 valley the general geological sections of the upper Paleozoic 



