COMPARISON WITH CRETACEOUS ROCKS OF 
OTHER COUNTRIES. 279 
striking contrast to the wide and flat grassy steppes of the Kalmucks fiom which 
we emerged. These rocks appeared to us to be identical in composition with 
those of the Volga, the Kalitva and the environs of Kursk. In truth they have 
been proved to be cretaceous, since M. le Play has detected the Pecten quinque-cos- 
tatus in their south-western prolongation 1 . 
In concluding this brief and imperfect sketch of the Cretaceous deposits we 
may remark, that they have a very wide extension in Southern Russia (pro- 
bably more extensive than is indicated in our Map), notwithstanding the com- 
paratively small number of points where white chalk appears at the surface 5 . We 
would also further remind our readers, of the agreements and discrepancies which 
this system exhibits in different parts of its range, when compared with deposits of 
the same age in Western Europe. If examined in detail the Russian type diflers, 
for the most part considerably, in lithological distribution from that of England 
and Northern France. It agrees, however, with that of Southern France, of Ger- 
many and parts of Poland, in the pure chalk being less equably deposited in thick 
masses. Thus at Lugan, in the south of Russia, the chalk having a thickness of 
600 or 700 feet, possesses all the characters of the English and French white chalk, 
and contains some of its characteristic fossils ; whilst at Kursk, as we have shown, 
it is reduced to a band only seven feet thick, intercalated between greensand and 
ironsand beneath, and earthy marls and sands above, which, however, occasionally 
contain true cretaceous fossils. In this mineral arrangement we perceive, however, 
that sort of general parallelism between the beds deposited in Russia and those in 
Western Europe (particularly with those of Eastern Germany), which we ought to 
expect to find in strata of the same epoch, separated from each other by wide in- 
tervals. Some persons may conclude, that the greensand beneath the white chalk 
is the exact counterpart, though on a small scale, of beds which are fully developed 
in the British Isles and Hanover, viz. the ferruginous or upper strata of t le ower 
greensand. Though we cannot affirm it, we would not reject this analogy, because 
the last researches of M. Jasikoff have shown the existence of variegated clays, in- 
ferior to the chalk properly so called, which contains an Ammonite of the upper 
part of the lower greensand (see note, p. 273). Additional detailed surveys may 
therefore, bring to light other lower greensand or Neocomian species in Russia 
. See Voyage dans la Russie M&idionde et la Crimea sous la direction de M. A. Demidoff, par M. le Play 
. The exact limits of the white chalk may indeed be easily defined by those who have the means of 
traversing the southern governments in various directions ; for in that country the superficial detritus » 
' i • iit- n.i i.aiv md the peasants are invariably acquainted with the 
not very thick, the ground is undulating and hilly, and tne pea.ams / , urches 
nearest points where the “ meol” or chalk is found, with which they whitewash their houses and churches. 
2 o 2 
