406 
WESTERN FLANK OF THE ARCTIC URAL. 
Another important geological result of the expedition of Captain Strajefski was 
the discovery, before alluded to (p. 230), of Jurassic strata replete with fossils in 64° 
north latitude. These beds on the banks of the little river Tol, were found to 
consist of greenish sand and dark shale, dipping to the east or from the Ural chain. 
Among the fossils are Pinna, Plagiostoma, Pholadomya, Modiola, &c., with Am- 
monites and Belemnites, forming altogether precisely the same group, with which 
■we had become familiar on the banks of the Moskva, the Oka and the Volga. 
The occurrence ot Jurassic rocks in this position was at first a great source of 
surprise to us, particularly as we had then observed no decisive proofs of a similar 
deposit in any portion of the eastern slopes of the Ural 1 . Subsequently, indeed, 
we were led to believe, that a small patch of Belemnitic strata, surrounded by erup- 
tive and metamorpliic rocks, and detected by Colonel Helmersen and M. Hoffman 
on the plateau of the Southern Ural near Tanalysk, might also be of this epoch. 
The strata of the same age on the eastern banks of the river Emba and its feeders, 
approaching as they do towards the southern prolongation of the Ural chain (see 
Map, PI. VI.), and apparently almost folding round it, would further lead us to 
conclude, that however the deposits are now separated, the sea in which the Juras- 
sic shells were entombed must have wrapped round the northern and southern ends 
of these mountains, and at a period long after their earliest elevations. Our ac- 
quaintance with these deposits has, indeed, been greatly extended by subsequent 
discoveries on the western flank of the Arctic Ural, where the same Oxfordian 
strata have been largely found, a point to which we shall presently revert. 
Western Flank of the Arctic Ural . — We now pass on to consider the structure 
of the boreal region, first laid open by our own researches®, which ranges north- 
wards from 62° north latitude, and constitutes the western flank of the Arctic Ural. 
The geological composition of the mountains, in these parallels, may be briefly ex- 
plained, by describing the natural sections exposed on the banks of the rivers 
which descend from the crest of the mountains. In that crest is situated the lofty 
mountain whence the magnificent Petchora takes its rise, its chief source being 
called by the native Zyrians Petcliora-ill-is (see Map). In summer this tract 
is frequented by a branch of the Ostiaks called Mantchi, who possess large 
' In a survey so expeditious as that which we made, it is not easy to establish the non-existence of a 
deposit over a wide region. We may, indeed, say that we found an imperfect shell in a mass of lime- 
stone immediately south of Verch Uralsk, which had much the appearance of an Ammonite of the Jurassic 
series. Of this, however, in the sequel. 
s See notice of the geological discoveries of our associate Count Keyserling, p, 230. 
