SECTION NEAR KURSK. 
269 
marlstones become calcareous, they have less of the conchoidal fracture of the 
“ Kiesel-thon,” are on the whole whiter, are occasionally iron shot, and con- 
tain certain corals (Choanites), which are certainly of the Cretaceous age, since 
they occur in the white chalk of England. Having already noticed these last- 
mentioned corals in Poland, we shall hereafter advert to them, as associated with 
other cretaceous fossils in white chalk, at Volsk upon the Volga. 
In following these beds to the city of Kursk, we became convinced that the 
whole of the argillo-siliceous and marnose group we had been examining, must 
be included in the Cretaceous system. In their range from Kharkof to Kursk, 
the beds becoming gradually more calcareous, show traces of animal life in pro- 
portion to an increase of lime. At Kursk we found, indeed, fossils in them which 
leave no doubt of the age of the deposit, such as a Belemnite, two species of Tere- 
bratulse, and the same Choanites already alluded to. This mass of chalk marls, 
having much the character of the upper greensand of England, is seen, on the banks 
of the rivers Sem and Tuskar, distinctly to overlie a course of pure white chalk 
without flints, of about seven feet in thickness, and containing Terebratulee, one 
of which resembles T. carnea. The detailed section from the banks of the Sem to 
the high ground on which stands the city of Kursk, is thus most valuable in clearly 
demonstrating, that the white chalk thins out in a system of sands and marls which 
are thus exhibited. 
GENERAL SECTION AT KURSK. 
40 . 
Black earth, &c. 
Drift. 
Sands occasionally ferruginous with concretions, passing downwards into 
sandy marls, &c. 
Chalk, marl, and “Kiesel-thon” with Terebratulae, a Belemnite, 
and Choanites. 
(Iron pyrites at intervals, and a course of yellow 
chalk marl at the base.) 
c White chalk with T erebratula carnea 
b. Ironstone shelly agglomerate . . . 
a. Green and yellow sands 
Level of the river 
The ironstone (section of 6) consists of a floor about four feet thick, of irregular mammillary concretions, 
so matted together as to form thick paving-stones, the interna, structure ot winch somewha resembles 
that of the clinkers in the lower greensand of English geologists (the car-stone of Norfolk, Bed ord &c.) 
A portion of this band is extensively quarried in galleries beneath the wh.te chalk, and is usually charged 
with (Mr**, the species of which is unknown to us. This bed of concretionary ironstone (the paving- 
stone of the city) does not exceed six inches to one foot in thickness, and occasionally lies in a mass ot 
true greensand, i. e. yellowish, incoherent, yellow sand, in which green particles are disseminated. 
2 N 
