292 Scientific Travellers. 



localities, particularly between Arzamas and Simbirsk, between 

 Syzran and Saratolt, at Saragula, and on the river Ilek near 

 Orenbourg. 



The upper oolitic group occurs in several situations along 

 the Donetz, where it was first recognized by Major Bliide. 

 It is calcareous, often oolitic, of light yellow colour, and 

 contains many Trigoiiice, Nerine<v, &c., which enable us to 

 compare it with the upper Jura of the Germans, or Port- 

 land and Coral rag division of my own country. 



The cretaceous system, though composed of very different 

 beds of marls, white chalk, sands and grits (sometimes green), 

 offers for the most part the fossils of the white chalk of Eu- 

 rope, such as the Inocernmi (Catillus), Bclemnites mucro- 

 natus, OstrcEa vesicularis, Terchratula earned-^. 



Above the cretaceous system, we have not been able to dis- 

 cover in any part of Russia, except in the Crimaea, the " num- 

 mulite limestone" which there sets on, and acquires a great 

 importance in its range through Georgia, Egypt, and the 

 Mediterranean basin. 



The equivalents of the lower tertiary formations (Eocene of 

 Lyell) seem to exist in one part only of your country (S. of 

 Saratoft). On the other hand, the middle and upper ter- 

 tiaries (Miocene and Pleiocene) cover large surfaces on the 

 Lower Volga, in Podolia, Volhynia, and also along the shores 

 of the Sea of Azof and the Black Sea, where the youngest of 

 these strata, very much resembling the "upper crag" of 

 Norfolk, are beautifully displayed. 



I have not time to enter upon the numerous and inter- 

 esting phoenomena of the Ural Mountains, the examination 

 of which occupied us nearly three months. We there studied 

 alternately the wonders of the gold alluvia, the sites of the 

 entombment of your great mammalia, and sought for the causes 

 of the astonishing metamorphism of the sedimentary rocks 

 of that chain. For an explanation of the last class of pbseno- 

 mena, the works of Humboldt and Gustaf Rose must always 

 be consulted. I will on this occasion simply say, that far from 

 he'in'^ primitive, as was supposed, this chain, with the excep- 

 tion of its eruptive masses, is entirely composed of Silurian^ 

 Devonian and Carbo7iiJeroiis rocks, more or less altered and 

 crystallized, but in which nevertheless we have been able to 

 recognise in a great number of localities my own Pentamerus 



* After this letter was written, we found in the collection of Professor 

 Eichwald at St. Petersburgh, a fine specimen of Exogyra and other fossils 

 in a green sandstone from the Lower Volga, sent to him from a locality well 

 known to us, which leaves little doubt of the existence also of a true re- 

 presentative of our greensand, — R. I. M. 



