OLDER TERTIARY ROCKS ON THE VOLGA. 
287 
The researches of M. Dubois have thus given us a clear line of demarcation 
between the older and middle tertiaries in respect to those regions w to 1 re as 
traversed , 
Though unable to continue with accuracy the comparison, from the western 
provinces described by M. Dubois, through the Ukraine, we may say from persona 
knowledge, that the same contrast exists between these northern and sou tern 
tertiary zones at the western and eastern extremities of the great region under 
consideration. At the western end, we have observed the siliceous and argilla. 
ceous tertiaries of the plains of Poland to be strikingly different from the calcareous 
shelly strata to the south of the axis of the Paheozoic rocks around Kielee (see 
Map). Again, far to the south-east, where we have no longer an Intel me .as 
granitic plateau, and where we may consider the great coal region of the Done tz 
to be the barrier of separation, all the younger deposits to the north of a re 
sandy and argillaceous, whilst those of the high steppe to the south are eminent y 
calcareous. Here, however, geological distinctions, founded upon foss, evidences 
are still wanting, for in the northern zone no naturalist has supplied them, an 
was only in a country much further to the east, viz. upon the V olga, below Saratof, 
that we obtained proofs of the existence of an older tertiary formation as ngi y 
determined by its organic remains. ^ . , . 
Unacquainted personally with any shelly tertiary deposits in the vast region lying 
between Butschak upon the west and the Volga on the east, we cannot pretend to 
draw the line of separation, except by general mineral characters anil we wd ^ 
terminate our brief sketeh of the older tertiary beds of Russia w. > a 
certain deposits in the neighbourhood of Simbirsk, and a description of the shelly 
strata at Antipofka on the Volga. c; m hirsk we are entirely in- 
For an acquaintance with deposits of this age ne of the govern- 
debted to M. Jasikoff, who states, that throughout a . grea P iUaceous 
meat of that name, the white chalk is covered by “;^“ ose ^ the 
sandstones, which are surmounted by ban s ones B argillaceous portion 
wbo,e having a thickness ol ^ £ocene ^ such as yw 
ot these deposits M. Jasiko and Tur MnoUa elliptica (Brongn.), 
tella imtrricataria (Lam.) , Nucu a com &(j The ove rlying sa „ds and 
with new species ol Ixucula, ’ Cvt herem and Dentalium, and much 
sandstones contain Pectunculus wtth Cjt heieie 
silieilied wood, often bored through by cylindrical bodies (Pholades^. 
