0. Schuchert — Russian Carboniferous and Permian. 31 



Russia show that we can not fix with certainty the exact 

 shore-lines of the sea of this epoch, still from the general dis- 

 tribution and the nature of the sediments of this time, when 

 compared with those of the Middle Carboniferous epoch, we 

 may conclude that there was a retreat of the sea in the west. 

 In the north the Upper Carboniferous sea had great extension 

 and communicated freely with the far-reaching Polar sea. In 

 the east it was limited by the Ural barrier, behind which in 

 Siberia lay a series of more or less extensive basins of brackish 

 or fresh water " (p. 679). 



For the sake of completeness, the reviewer will here intro- 

 duce a somewhat detailed generalized section of the Permian 

 and Carboniferous of Russia, compiled from various recent 

 sources :* 



Brackish ? Permian or ?Triassic, Tartarian (PT). 



Red grits, argillaceous sands, and intercalations of clay and 

 marl of the same color ; rarely green or bright blue. 



Red colored marls and variegated clays, with intercalations of 

 grayish grits and sands of the same tints. 

 These two groups have brackish-water genera, as TJnio, 

 Antliracosia, Najadites, and Paloeomutela. 



Permian (P) of Samara and Oufa (the Permian sensu-stricto of 



Murchison). 



Brown grits, marls, and limestone. 



Has some pelecypods, as Allorisma elegans, etc. 



Gray slaty limestones, with intercalated marls and friable grits. 

 Has Murchisonia subangulata, Turbonilla altenbur gen- 

 sis, Macrodon Jcingianum, Osteodesma kutorgana, Modi- 

 olopsis pallasi, Leda speluncaria, etc. Of Crustacea, 

 Bairdia, Estheria. Lingula orientalis. Of fishes, Palce- 

 oniscus, Acrolepis. 



Grits and gray limestone, more or less copper-bearing. 



Rich in brachiopods : Spirifer regulatus, Spiriferina 

 cristata, Athyris pectinifera, Dielasma elongata, Pro- 

 ductus cancrini, P. hemisphcerious, Strophalosia hores- 

 cens. Some bivalves and corals. 



Red argillaceous grits, with intercalations of clay and gray, 

 brown, and reddish marls. 



Fossiliferous only in the higher beds: Productus can- 

 erini, Athyris pectinifera, Pielasma elongata, Allorisma 

 elegans, Macrodon Itingianum, etc. 



*The Permian and Moscowian section is taken from Nikitin — " De 

 Moscoua Oufa (via Miatschkowo, Riazan, Penza, Syzran, Samara)," Guide des 

 Excursions, VII, Congres Geol. Internat., 1897, Pt. II ; the Uralian, from 

 Tsckernyschew's great brachiopod work here reviewed ; the Viseian and 

 Artinsk, from Tschernyschew, Mem. du Comite Geol., Ill, No. 4, 1889. 



