Page:A Treatise on Geology, volume 1.djvu/177

 CHAP. VI. Rhine and Moselle, and are largely developed in Russia. 'They pass Livonia by the Lakes of Ilmen and the Waldai hills, and are extended over a vast region to the N. E., where they constitute a large portion of the shores of the White Sea.'

Analogous in mineral aspect to the old red formations of England, they contain, together with the characteristic fishes of Scotland and the brachiopoda of the formations as seen in Devonia, Westphalia, and Belgium; but they contain, in addition, salt springs and gypsum. A dome-like elevation of Devonian rocks (800 feet) occurs in the centre of European Russia, (Orel, Voroneje), full of fishes and mollusca imbedded in yellow and white marl stone and limestone.

The changes to which geological classification is reasonably liable appear in nothing more conspicuous than in the division of the great carboniferous system, as it was expounded by Conybeare (1829), into two systems, the lower being formed of the old red sandstone, as it appears on the borders of Wales, Cumberland, the Lammermuirs, and Grampians, and in a quite different form in North and South Devon. In the former districts the old red is still very poor in organic life, except in the class of fishes; but the Devonian series, poor in fishes, is rich in zoophyta, mollusca, and crustacean. As it is mainly by palæontological evidence that modern geology is guided, the now prevalent term for these strata is the Devonian system, which is found to be represented extensively in European Russia and North America, and probably in Africa. The fauna of the Devonian beds is certainly distinguishable from that of the rocks above and below: it has enough of an intermediate character to complete the harmony of the palæozoic groups, and yet enough of distinctiveness to demand an independent place.

This place was not assigned till after many examinations of the characteristic fossils of South Devon, of which some were first figured by Mr. Sowerby (Min.