| | White Konjeprus | stones. |
O | +-------------+-------------------+------------------------------+--------------+ Limestone with | |
N | | Gedinnien |Slates of St Hubert| Slates of Gedinne. | Slates and | Hercynian | |
I | | | and Fooz, slates | | quartzites | fauna. | |
A | | | of Mondrepuits, | | of Plou- | | |
N | | | arkose of Weis- | | gastel. | | |
. | | | mes, conglomerate | | | | |
| | | of Fepin. | | | | |
\ +-------------+-------------------+------------------------------+--------------+-----------------+-----------------+

The chief interest of the Russian rocks of this age lies in the fact,
first signalized by Murchison and his associates, that they unite
within themselves the characters of the Devonian and the Old Red
Sandstone types. In some districts they consist largely of limestones,
in others of red sandstones and marls. In the former they present
molluscs and other marine organisms of known Devonian species; in the
latter they afford remains of fishes, some of which are specifically
identical with those of the Old Red Sandstone of Scotland. The
distribution of these two palaeontological types in Russia is traced
by Murchison to the lithological characters of the rocks, and
consequent original diversities of physical conditions, rather than to
differences of age. Indeed cases occur where in the same band of rock
Devonian shells and Old Red Sandstone fishes lie commingled. In the
belt of the formation which extends southwards from Archangel and the
White Sea, the strata consist of sands and marls, and contain only
fish remains. Traced through the Baltic provinces, they are found to
pass into red and green marls, clays, thin limestones and sandstones,
with beds of gypsum. In some of the calcareous bands such fossils
occur as _Orthis striatula_, _Spiriferina prisca_, _Leptaena
productoides_, _Spirifer calcaratus_, _Spirorbis omphaloides_ and
_Orthoceras subfus