544 PK0F. PAVL0W Off THE CLASSIFICATION OF THE [Aug. 1 896, 



merit, in trie government of Eiasan, and these were at the same 

 time studied by M. Bogoslowsky. 1 



As the result of these researches, I am now enabled to give a 

 more complete and correct scheme of the Upper Jurassic and Lower 

 Cretaceous succession in Russia, or, in otlier words, in the Boreal 

 province. The study of the close of the Jurassic and the beginning 

 of the Cretaceous times in this region helps largely in the deter- 

 mination of the position of the different horizons of the same series 

 in other countries, especially in England and Germany ; and the 

 further working out of the common classification of these beds may 

 be thus facilitated. 2 



The grounds on which this new scheme is based are as follows. 

 My researches near Kashpur, in the district of Syzran, have 

 shown that below the horizon of Polyptychites polyptychus, Key- 

 serlingi, syzranicus, and between this horizon and the zone of Cras- 

 pedites kashpuricus and Oxynoticeras subclypeiforme, there exists a 

 bed of sandy marl (about 1 metre in thickness) very rich in Aucella, 

 especially Aucella volgensis. This bed, which has both above and 

 below it a small seam of glauconitic sand, includes (along with some 

 fossils proper to the zone of Polyptychites Keyserlingi) a series of 

 especially characteristic forms, which are known also from the 

 before-mentioned bed in the districts of Alatyr and Kurmysh, 

 including Ammonites stenomphalus and Marcousanus. Owing to 

 the close relations of the bed with the zone of Polyptychites Keyser- 

 lingi, I find it convenient to unite it therewith, and to apply to 

 both the name of the Petchorian Series ; and this is the more 

 convenient, since, judging from a collection of fossils not yet de- 

 scribed, brought to me by M. A. Ivanow from the region of Petchora, 

 and also from some literary data, both faunas exist there in 

 closely related beds. At Kashpur both the lower and the upper 

 zones of the Petchorian Series can be distinguished, and both are 

 rich in Belemnites lateralis, subquadratus, and russiensis. In the 

 districts of Kurmysh and Alatyr only the lower zone has been dis- 

 covered, and M. Stchirowsky, who has described a part of its fauna, 

 has recorded therein such forms as Oxynoticeras Gevrilianum and 

 Marcousanum, which are generally regarded as Lower Neocomian. 

 Such forms are, however, very rare among the numerous and entirely 

 new species of ammonites, more or less nearly related to Ammonites 

 stenomphalus. (I am now engaged in describing this remarkable 

 fauna.) 



The presence, though very rare, of Lower Neocomian types in 

 this zone is an argument in favour of considering the whole 



1 A. Pavlow, ' On the Mesozoic Beds of the Government of Eiasan,' Report 

 of the Geological Excursion undertaken in the summer of 1893, Scient. Rec. 

 Imp. Univ. Moscow, sect. Nat. Hist. pt. ii. (in Russian) ; N. Bogoslowsky, 

 ' Volgian, Upper Tithonic, and Neocomian Beds in the Government of 

 Riasan,' Preliminary Report, Materialen zur Geoiogie Russlands, vol. xvii. 

 1895 (in Russian). 



2 The correlation of these beds in the different countries of Europe was 

 the subject of a communication made by me to the International Geological 

 Congress at Zurich in 1894. 



