252 
CORAL RAG AND CALC GRIT IN POLAND AND RUSSIA. 
group is then overlaid by green sandstone, sands, &c., which in their turn are sur- 
mounted by chalk. To the consideration of the last-mentioned deposits we shall 
return in the next chapter. 
SECTION AT IZIUM. 
39 . 
m. White chalk 
1. Hard quartzose grit, with siliceous cement 
k. Sandy clay, &c 
j. Green sandstone, with siliceous concretions 
*. Porous light-coloured sandstone, with tripoli and yellow sand 
h. Grey sandstone and sand, with green grains and courses of marl . . . , 
g. Three beds of limestone, with small univalves and Nerinceee 
f. Fine-grained oolite in a base of compact limestone 
e. Soft yellow limestone, with Gervlllm * 
d. Limestone, very hard and compact, slightly translucent, occasionally 
containing gypseous courses and a few fossils 
c. Marls and shelly agglomerates, with T rigonia clavellata and Cida- 
rites TUumrnbachii 
b. Band of fine oolitic structure 
a. Beds obscured by alluvia. Sands with plants ... . 
Level of the Donetz. . , 
There is, then, as we have shown, the most perfect agreement between these 
sections in different parts of the Donetz. The higher inclination of the strata 
visible in one spot near Kamenka, is proved to he, after all, a mere local derange- 
ment, since at distances of ten and more versts apart, we observed the same beds 
in nearly horizontal positions. The persistence of the shelly agglomerates with 
Trigonia clavellata and the fine-grained oolite, afford, in short, as clear a line of 
geological horizon, though on a smaller scale, as the Inoceramus sandstone in the 
lower Jurassic division of other parts of Russia. We again detected these beds 
occupying the right hank of the river, in low cliffs from fifteen to thirty feet high, 
at Donetzkaya, near Petrofskaya, where, in addition to the Trigonia clavellata and 
Nerincea elegans (Fischer), the Ammonites triplex also occurs : there is also present a 
remarkable Ammonite of undescribed species, which M. D’Orbigny informs us 
exists in the coral rag of France'. 
From the details here given, and from the section which shows that these strata 
repose upon ferruginous sands with plants, and are overlaid by green sand and 
chalk, our readers can have no doubt that the group which we are describing, is 
of age posterior to the dark Jurassic shales and sands of the central and northern 
regions. But can we refer them with precision to any one known formation or 
subformation of the oolitic series of England, or of the Jura limestone of the Con- 
This Ammonite approaches to the A. biplex. 
