T1IK CAIMinNlFHKors SYSTKM 319 



The following is a tabular view of the strata in the Pilsen 

 basin, modified from that given by Feistmantel : 10 



p /Red felspathic sandstones with Araucaritea. 



\Shalus witli ironstone nodules (Permian plants). 



? Shales with Carboniferous plants, a coal-seam and the 

 Stephauian- Nurschau "gas-coal" (oil-shale). 



(Lower shales with a coal-seam. 



The plants in the Stephanian shales include Catamites (three 

 species), Sphenopteris Schlotheimi and eight other species, Odontopterit 

 obtusiloba, Dictyopteris Brongniarti, Siyillaria distans, and fragments 

 of lyalchia. Both Feistmantel and Romer correlate these beds 

 with those of the Ottweiler Group. Further particulars will be 

 found in the paper referred to. 



B. URALIAN FACIES 



1. The Fauna. This is entirely marine in the more typical 

 areas. Foraminifera play an important part in the formation of 

 Uralian limestones, the principal genera being Fusulina, Swagerina, 

 and Doliolina. A spiral Bryozoan, Archimedes, is also a common 

 and characteristic fossil. Brachiopoda are abundant, especially 

 the Terebratuloid Dielasma, the Rhynchonellid Camarophoria, 

 and the Orthotetid Meekella. Spirifers are still common, and the 

 persistent species Productus cora is abundant ; Chonetes is represented 

 by G. uralicus, and shells of the genus Spiriferina make their appear- 

 ance, together with some which are closely allied to JValdheimia. 



Of Mollusca the Lamellibranchs Conocardium, Aviculopecten, 

 Schizodus, and other Carboniferous genera occur. The Gastropod 

 Omphalotrochus is common, but Cephalopoda are not numerous ; 

 Gastrioceras marianum occurs throughout, and in the highest beds 

 Agathiceras uralicum appears. A few trilobites also survive. 



2. Stratigraphy. The typical development of this series is 

 found on the south-west side of the Urals in the basin of the river 

 Ai (Province of Ufa), where the whole consists of limestone, and 

 three stages or zones are recognised by Tschernyschew, viz. : 



3. Zone of Swagerina princeps and Spirifer sarana. 

 '2. Zone of Productus cora and Meekella eximia. 

 1. Zono of Omphalotrochus Whitneyi. 



The same succession is found in the Moscow basin and in the 

 Tinian district in the north of Russia. The limestones of the 

 middle zone are generally dolomitic. 



On the eastern slopes of the Ural Mountains there is a much 

 greater variety of sediments indicating the near proximity of land, 



