+---------------------------------+-----------------+------------------+-----------------------------+
| North-West Russia. | Central Russia. | Petchoraland. | Ural Region. |
/ +---------------+-----------------+-----------------+------------------+-----------------------------+
U | | Red sandstone | Limestones with | Limestones with | Domanik slates | Cypridina slates, Clymenia |
P | | (Old Red). | Spirifer | Arca oreliana. | and limestones | limestones (Famennien). |
P < | | Verneuili and | Limestones with | with Sp. | Limestones with Gephyoceras |
E | | | Sp. Archiaci. | Sp. Verneuili | Verneuili. | intumescens and |
R | | | | and Sp. | | Rhynchonella cuboides |
| | | | Archiaci. | | (Frasnien). |
\ +---------------+-----------------+-----------------+------------------+-----------------------------+
M / | Dolomites and limestones | Marl with | Limestones and slates with |
I | | with | Spirifer Anossofi | Sp. Anossofi (Givétien). |
D < | Spirifer Anossofi. | and corals. | Limestones and slates with |
D | | | Pentamerus baschkiricus |
L | | Lower sandstone (Old Red). | (Eifélien). |
E \ +---------------+-----------------+-----------------+------------------+-----------------------------+
/ | | | | Limestones and slates of |
L | | | | | the Yuresan and Ufa rivers,|
O | | Absent. | | | slate and quartzite, |
W < | | | | marble of Byclaya and |
E | | | | | of Bogoslovsk, phyllitic |
R | | | | | schists and quartzite. |
\ +---------------+-----------------+-----------------+------------------+-----------------------------+
The Lower Devonian of the Harz contains a fauna which is very
different from that of the Rhenish region; to this facies the name
"Hercynian" has been applied, and the correlation of the strata has
been a source of prolonged discussion among continental geologists. A
similar fauna appears in Lower Devonian of Bohemia, in Brittany
(limestone of Erbray) and in the Urals. The Upper Devonian of the Harz
passes up into the Culm.
In the eastern Thuringian Fichtelgebirge the upper division is
represented by _Clymenia_ limestone and _Cypridina_ slates with Adorf
limestone, diabase and Planschwitzer tuff in the lower part. The
middle division has diabases and tuffs at the top with Tentaculite and
Nereite shales and limestones below. The upper part of the Lower
Devonian, the sandy shale of Steinach, rests unconformably upon
Silurian rocks. In the Carnic Alps are coral reef limestones, the
equivalents of the Iberg limestone, which attain an enormous
thickness; these are underlain by coral limestones with fossils
similar to those of the Konjeprus limestone of Bohemia; below these
are shales and nodular limestones with goniatites. The Devonian rocks
of Poland are sandy in the lower, and more calcareous in the upper
parts. They are of interest because while the upper portions agree
closely with the Rhenish facies, from the top of the Coblentzien
upwards, in the sandy beds near the base Old Red Sandstone fishes
(_Coccosteus_, &c.) are found. In France Devonian rocks are found well
developed in Brittany, as indicated in the table, also in Normandy and
Maine; in the Boulonnais district only the middle and upper divisions
are known. In south France in the neighbourhood of Cabrières, about
Montpellier and in the Montagne Noire, all three divisions are found
in a highly calcareous condition. Devonian rocks are recognized,
though frequently much metamorphosed, on both the northern and
southern flanks of the Pyrenees; while on the Spanish peninsula they
are extensively developed. In Asturias they are no less than 3280 ft.
thick, all three divisions and most of the central European
subdivisions are present. In general, the Lower Devonian fossils of
Spain bear a marked resemblance to those of Brittany.
_Asia._--From the Ural Mountains eastward, Devonian rocks have been
traced from point to point right across Asia. In the Altai Mountains
they are represented by limestones of Coblentzien age with a fauna
possessing Hercynian features. The same features are observed in the
Devonian of the Kougnetsk basin, and in Turkestan. Well-developed
quartzites with slates and diabases are found south of Yarkand and
Khotan. Middle and Upper Devonian strata are widespread in China.
Upper Devonian rocks are recorded from Persia, and from the Hindu Kush
on the right bank of the Chitral river.
_England._--In England the original Devonian rocks are developed in
Devon and Cornwall and west Somerset. In north Devonshire these rocks
consist of sandstones, grits and slates, while in south Devon there
are, in addition, thick beds of massive limestone, and intercalations
of lavas and tuffs. The interpretation of the stratigraphy in this
region is a difficult matter, partly on account of the absence of good
exposures with fossils, and partly through the disturbed condition of
the rocks. The system has been subdivided as shown in Table III.