728 
Strajesski as far as even 65° N. lat. on the eastern flanks of the Ural 
chain. 
The upper members of the Jurassic system, as exhibited in the 
South of Russia, near Izium, where they were first recognised by 
Major Bloéde, differ both lithologically and zoologically from the 
dark shales and sands of the northern and central regions. They 
are chiefly light-coloured limestones and marls, and are charged 
with large Ammonites, resembling those of the Portland rock with 
Trigonia clavellata, Nerinee, and other types closely allied to those 
which occur in the upper oolites of Great Britain and the Continent. 
Cretaceous System.—This system is very considerably developed 
in the central and southern tracts of Russia, In the government of 
Simbirsk, where it has been closely studied and its fossils carefully 
collected by M. Jasikof, it surmounts the Jurassic series, and the 
same order may be seen in the governments of Saratof and on the 
banks of the Donetz near Izium. . 
Though the lithological sequence of the strata differs from that 
of the British Isles, the system, as a whole, bears striking analogies 
to that of the same age in Western Europe. The white chalk, for 
example, and many of the fossils which it contains, including Jno- 
ceramus Cuvieri, Belemnites mucronatus and Gryphea vesiculosa, is 
absolutely undistinguishable from that of France and England ; but 
in the localities seen by the authors, it did not offer the same sub- 
jacent succession of gault and lower greensand, as in Western 
Europe, though at Kursk the white chalk reposes on hard concre- 
tionary sandy ironstone, somewhat resembling the clinkers of the 
lower greensand of England. Nor are there any evidences of the © 
existence beneath the cretaceous rocks of the ‘“‘Systéme Néoco- 
mien” of the French geologists. Associated however with the 
white chalk, the authors observed, particularly between Saratof 
and Tzaritzin, many beds of marl and siliceous clay-stone, in which 
bodies like Alcyonice were prevalent, and at Kursk they found that 
the white and yellowish subcalcareous marls which closely overlaid 
the white chalk contained a Belemnite, as well as certain polypifers 
common to the true white chalk of other parts of Russia ( Volsk), 
and hence they concluded, that some of these overlying marls are 
possibly the representatives of the Maestricht beds of Europe, 
The white chalk alone has been pierced to a depth of upwards of 
600 feet by an artesian shaft at the iron forges of Lugan, in South- 
ern Russia, in which tract the deposit lies unconformably on the 
uplifted edges of the carboniferous rocks. 
Tertiary Deposits.—The tertiary strata, as separated from diluvia] 
and alluvial accumulations, are little known in the North of Rus- 
sia, with the exception of the shelly strata of post-pliocene age 
which have been described in the government of Archangel (anté, 
p. 404). . 
- The lowest tertiary beds which the authors personally examined, 
are the marls with concretions forming cliffs at Antipofka, on the 
right bank of the Volga below Saratof, where they were-first noticed 
by Pallas. Among these shells are several species undistinguishable 
