EUROPEAN EQUIVALENTS OF THESE JURASSIC ROCKS. 
253 
tinent ? Even whilst on the spot, we were led rather to group them with the 
coral rag than with any inferior stratum. We subsequently confirmed this view 
by a visit to Poland, and can now state, that the rocks of the Donetz may be 
well compared with the white limestone on which the citadel of Cracow stands. 
Forming a low ridge along the banks of the Vistula near that city, the upper mass 
is there a white, compact limestone, about 300 feet thick, which, as it contains 
lines of flint exactly resembling those of the English chalk, was formerly placed 
on the parallel of that formation. The lower strata are yellowish, sandy, calca- 
reous grits. In the white or superior beds, Professor Zeuschner, with whom we 
recently examined the rock in situ, has identified the following fossils of the coral 
rag, — viz. Scyphia clathrata (Goldf.), Ammonites biplex, A. triplex, A. polyplocus, A. 
annularis, A. jlexuosus, A. vertebralis, Lima proboscidea, Terebratula biplicata, and 
T. subsenilis. The lower mass, from 100 to 150 feet thick, contains Pecten Jibrosus, 
P. lens, P. textorius, P. vimineus, Terebratula varians, T. concinna, T. bullata or glo- 
bata (V. Buch), T. perovalis, Lima proboscidea, and L. pectinoides ? , with some 
broken Belemnites and Fucoids. 
Judging from these organic remains, Professor Zeuschner correctly places the 
beds which contain them, in parallel, as a whole, with the coral rag. We may add, 
however, that, in our opinion, the lowest of these hands also truly represents the 
calcareous grit of Oxford and the Malton oolite of Yorkshire, since it contains 
some of the most characteristic species of that subformation, — a very remarkable 
coincidence, when we consider the distance which separates Malton and Oxford 
from Cracow. But to resume and apply this reasoning to Russia, we may say, that 
the Polish beds of Southern Poland serve as a valuable connecting link between 
England and Russia, since they possess, in common with the limestones of the 
Donetz, the same characteristic Ammonites biplex, and we therefore believe, that 
they both belong to the same group — the upper Oxford oolite. 
Conclusion. — In terminating this chapter, we may repeat, that our observations 
have established and extended the view first taken by M. Von Buch, from an in- 
spection of the fossils only ; that in a broad zone, extending from the plains of 
Prussia into the distant tracts of Russia, all the Jurassic strata belong to the Ox- 
fordian formation of that series. We have further ascertained, that in Central 
Russia, as in Poland, there exists an arenaceous deposit, with plants and occa- 
sional lignite, which represents the sands in and above the Oxlord clay ; whilst 
in Southern Russia a small upper member of the series is the equivalent of the 
2 L 
