276 
SANDY AND ARGILLACEOUS MEMBERS OF THE GROUP. 
42 , 
S.S.E, 
Ussa rocks, 
N.N.W. 
d. White quartzosc siliceous grit, with leaves of dicotyledonous plants. 
c. Sands, clay and marl,— beds obscured in sandy slopes. 
b. Sandstone, sand and white marlstone, with Alcyonic forms and ironstone concretions. 
a. Hard, porcellaneous, bluish-grey claystone and marlstone (conclioidal fracture). 
But here it is essential to point out to our readers, that the same siliceous 
marlstone and sandstone with Alcyonia, which near Saratof we have shown to 
occupy a plateau, descend atKamischine to low cliffs upon the Volga, where they 
are surmounted by tertiary grits. In these relations, therefore, as well as in the 
gradual disappearance of the Jurassic strata beneath the chalk, we have the 
clearest proofs, that in following the course of the Volga from Saratof, or from 
north to south, the older formations successively disappear beneath the younger. 
The beds of this series, which have the most persistent character, are dingy 
white claystone of very low specific gravity, with ferruginous concretions and 
some grains of greensand, which are seen to repose on a similar rock of equally 
compact structure and conchoidal fracture, — a porcellanite, in which greensand 
concretions occur at intervals. In a tvord, these rocks on the level of the Volga 
at Kamischine, are undistinguishable from the beds which near Volsk and Saratof 
are several hundred feet above that stream ; for they contain Alcyonic-like bodies 
having stems and heads, usually in very decisive green sandstone and with some 
imperfect corals. We may also remark, that Exogyne imbedded in greensand occur 
in this region, specimens of which were sent to Professor Eichwald, who submitted 
them to our inspection on our return to St. Petersburgh l . 
Still further to the south we found similar argillaceous and sandy beds, with 
concretions of greensand and mottled, porcellaneous, greenish marlstone, in parts 
having a cretaceous aspect, with overlying sands and quartzose sandstone ; and at 
the post-station of Bielaya-glina, thirty versts south of Kamischine, we again met 
with pure white chalk, rising into hills and exposed in ravines, at nearly the same 
level, and at a very short distance from the sandstone, claystone and marl we have 
been considering. In these chalk beds were several fossils, including corals and 
Terebratula earned. 
1 It was stated that these Exogyrae were found between Kamischine and I zaritzin ; but the locality 
was not mentioned. One of the Exogyrm bears certainly a strong resemblance to a species common in 
the Maidstone grits or upper part of the lower greensand of England, and is associated with a small Pla- 
giostoma, a Pecten very near to P. orbicularis, Vermetus, &c. 
