obtained from the Lower Devonian “Nereitenschichten” of Thuringia. The characteristic Holoptychius nobilissimus has been detected in the Psammite de Condroz, which in Belgium forms a characteristic sandy portion of the Upper Devonian rocks. These are interesting facts, as helping to link the Devonian and Old Red Sandstone types together. But they are as yet too few and unsupported to warrant any large deduction as to the correlations between these types.
It is in the north-east of Europe that the Devonian and Old Red Sandstone appear to be united into one system, where the limestones and marine organisms of the one are interstratified with the fish-bearing sandstones and shales of the other. In Russia, as was shown in the great work Russia and the Ural Mountains by Murchison, De Verneuil and Keyserling, rocks intermediate between the Upper Silurian and Carboniferous Limestone formations cover an extent of surface larger than the British Islands. This wide development arises not from the thickness but from the undisturbed horizontal character of the strata. Like the Silurian formations described elsewhere, they remain to this day nearly as flat and unaltered as they were originally laid down. Judged by mere vertical depth, they present but a meagre representative of the massive Devonian greywacke and limestone of Germany, or of the Old Red Sandstone of Britain. Yet vast though the area is over which they form the surface rock, it is probably only a small portion of their total extent; for they are found turned up from under the newer formations along the flank of the Ural chain. It would thus seem that they spread continuously across the whole breadth of Russia in Europe. Though almost everywhere undisturbed, they afford evidence of some terrestrial oscillation between the time of their formation and that of the Silurian rocks on which they rest, for they are found gradually to overlap Upper and Lower Silurian formations.
Table I.
| Stages. | Ardennes. | Rhineland. | Brittany and Normandy. |
Bohemia. | Harz. | |
| Upper Devonian. |
Famennienc (Clymenia beds). |
Limestone of Etrœungt. Psammites of Condroz (sandy series). Slates of Famenne (shaly series). |
Cypridina slates. Pön sandstone (Sauerland). Crumbly limestone (Kramen- zelkalk) with Clymenia. Neheim slates in Sauerland, and diabases, tuffs, &c., in Dillmulde, &c. |
Slates of Rostellec. | Cypridina slates. Clymenia limestone and limestone of Altenau. | |
| Frasnien (Intumes- cens beds). |
Slates of Matagne. Limestones, marls and shale of Frasne, and red marble of Flanders. |
Adorf limestone of Waldeck and shales with Goniatites (Eifel and Aix) = Budesheimer shales. Marls, limestone and dolomite with Rhynchonella cuboides (Flinz in part). Iberg limestone of Dillmulde. |
Limestone of Cop- Choux and green slates of Travuliors. |
Iberg limestone and Winterberg lime- stone; also Adorf limestone and shales (Budesheim). | ||
| Middle Devonian. |
Givérien (Stringo- cephalus beds). |
Limestone of Givet. | Stringocephalus limestone, ironstone of Brilon and Lahnmulde. Upper Lenne shales, crinoidal limestone of Eifel, red sandstones of Aix. Tuffs and diabases of Brilon and Lahnmulde. Red conglomerate of Aix. |
Limestones of Chalonnes, Montjean and l'Ecochère. |
H2 (of Barrande) dark plant-bearing shales. H1. |
Stringocephalus shales with Flaser and Knollenkalk. Wissenbach slates. |
| Eifélien (Calceola beds). |
Calceola slates and limestones of Couvin. Greywacke with Spirifer cultrijugatus. |
Calceola beds, Wissenbach slates, Lower Lenne beds, Güntroder limestone and clay slate of Lahnmulde, Dillmulde, Wildungen, Griefenstein limestone, Ballersbach limestone. |
Slates of Porsguen, greywacke of Fret. |
G3 Cephalopod limestone. G2 Tentaculite limestone. G3 Knollenkalk and mottled Mnenian limestone. |
Calceola beds. Nereite slates, slates of Wieda and lime- stones of Hasselfeld. | |
| Lower Devonian. |
Coblentzien | Greywacke of Hierges. Shales and conglomer- ate of Burnot with quartzite, of Bierlé and red slates of Vireux, greywacke of Vireux, greywacke of Montigny, sand- stone of Anor. |
Upper Coblentz slates. Red sandstone of Eifel, Coblentz quartzite, lower Coblentz slates. Hunsrück and Siegener greywacke and slates. Taunus quartzite and greywacke. |
Limestones of Erbray, Brulon, Viré and Néhou, greywacke of Faou, sandstone of Gahard. |
F2 of Barrande. White Konjeprus Limestone with Hercynian fauna. |
Haupt quartzite (of Lossen) = Rammelsberg slates, Schallker slates = Kahleberg sandstone. Hercynian slates and limestones. |
| Gédinnien | Slates of St Hubert and and Fooz, slates of Mondrepuits, arkose of Weismes, conglomerate of Fèpin. |
Slates of Gédinne. | Slates and quartzites of Plougastel. |
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 subfusiforme. In the higher beds Holoptychius and other well-known fishes of the Old Red Sandstone occur. Followed still farther to the south, as far as the watershed between Orel and Voronezh, the Devonian rocks lose their red colour and sandy character, and become thin-bedded yellow limestones, and dolomites with soft green and blue marls. Traces of salt deposits are indicated by occasional saline springs. It is evident
