todtliegende refers to the rocks being red, and dead as regards copper yielding.

Walchia piniformis, Schloth. Permian, Saxony. (Gutbier, Die Versteinerungen des Permischen Systemes in Sachsen, vol. ii. pl. x.) Nat. size.

a. Branch.

b. Twig of the same.

c. Leaf magnified.

Fig. 429.

In Russia the nearly horizontal strata of the Permian, cover vast areas, and consist of sandstones, marls, shales, and thin seams of coal, conglomerates, limestones, and rock-salt and gypsum beds. In the lower half of the strata Calamites, Cyclopteris, and Pecopteris appear. Palæoniscus and Labyrinthodonts have been found, and the marine beds contain Productus horridus and Productus cancrini.

Permian Flora.-About 18 or 20 species of plants are known in the Permian rocks of England. None of them pass down into the Carboniferous series, but several genera, such as Alethopteris, Neuropteris, and Walchia, are common to the two groups. Caulopteris, Lepidodendron, Calamites, and Sternbergia

are lower Permian and Carboniferous genera, and fragments of coniferous wood have been found with them, The Permian flora on the Continent appears, from the researches of MM. Murchison and De Verneuil in

Fig. 428.

Cardiocarpon Ot

tonis. Gutbier.

Permian, Saxony.

diameter.

Russia, and of MM. Geinitz and Von Gutbier in Saxony, to be moderately distinct from that of the Coal, 50 species being 5 Murchison's Russia, vol. ii. pl. A, fig. 3.

common to both formations. But the Permian flora is characterised by the genus Callipteris, which is not Carboniferous, and by a profusion of tree-ferns of the genus Psaronius, of Equisetites, and by abundance of Walchix (fig. 427).

In the Permian rocks of Saxony no less than 60 species of fossil plants have been met with. Two or three of these, as Calamites gigas, Sphenopteris erosa, and S. lobata, are also met with in the Government of Perm, in Russia. Seven others, and among them Neuropteris Loshii, Pecopteris arborescens, and P. similis, and several species of Walchia (see fig. 427), a genus of Conifers called Lycopodites by some authors, are said by Geinitz to be common to the coal-measures.

Among the Permian genera, are the fruit called Cardiocarpon (see fig. 428), Asterophyllites, and Annularia, so characteristic of the Carboniferous period; also Lepidodendron and Calamites; also Noeggerathia (fig. 429), the leaves of which have parallel veins without a mid-rib, and to which various generic synonyms, such as Cordiates, Flabellaria, and Poacites, have been given, is another link between the Permian and Carboniferous vegetation. Coniferæ, of the Araucarian division, also occur; but these are likewise met with both in older and newer rocks. The plants called Sigillaria and Stigmaria, so marked a feature in the Carboniferous period, are as yet wanting in the true Permian.

Among the remarkable fossils of the Rothliegendes, or lowest part of the Permian in Saxony and Bohemia, are the silicified trunks of tree-ferns called generically Psaronius. Their bark was surrounded by a dense mass of air-roots, which often constituted a great addition to the original stem, so as to double or quadruple its diameter. The same remark holds good in regard to certain living extra-tropical arborescent ferns, particularly those of New Zealand.

Thus we see that while, upon the whole, the plants of the Marl-slate or Middle Permian, differ from those of the Coal Period, the plants of the Rothliegende of Germany which belong to the Lower Permian begin to show a very close generic affinity with Carboniferous forms.

In the basins of Pilsen and Rakowitz in Bohemia, the flora of the strata is Carboniferous, but the fauna is decidedly like that of the Permian series. These strata, which are called Permo-carb., have yielded 43 species of Amphibians, some with the gills still visible. Corresponding strata at Autun, in France, have yielded additional kinds of Amphibia to the researches of Gaudry.

The Permian formation is hardly represented in America,

but it is possible that the Upper barren-measures' of the Appalachian coal-fields belong to it, on account of the existence of Permian and later types of plants, and the comparative absence of the true Carboniferous flora.

CHAPTER XXIV.

THE CARBONIFEROUS FORMATION.

Principal subdivisions of the carboniferous formation-Coal-measures, grits, limestones, and shales-The divisions in Somerset and South Wales, in the North of England and Scotland and Ireland-Deposition of the formation-Crust movements at the close and after the Permian-Coal basins -Coal-fields and measures-Coal formed on land-Coal trees-Gannister coal water-borne-Nova Scotia coal-measures exemplifying the development of the division-Vegetation of coal period-Ferns-Lycopodiace Equisetacea Sigillaria-Stigmaria-Conifera - Monocotyledons-Climate of the coal period.

Principal Sub-divisions of the Carboniferous Formation. -The next formation we meet with in descending order, is the Carboniferous, commonly called the 'Coal;' because it contains many beds of that mineral in a more or less pure state, interstratified with sandstones, shales, and limestones. The coal itself, even in Great Britain, where it is most abundant, constitutes but an insignificant portion of the whole group. Thus in one part of the Carboniferous formation, the true 'Coal-measures,' in South Wales, which attain the thickness of from 2,500 to 11,000 feet, the aggregate thickness of the various coal-seams is only about 180 feet. But although the Carboniferous formation consists of several divisions, coal and coal plants are found in each; and this gives a solidity to the conception of the nature of the living things which have left their fossil remains in the deposits of the whole formation.

The Carboniferous formation assumes various characters in different parts of England, Wales, and Scotland, and usually comprises terrestrial and marine deposits. The uppermost strata are the Coal-measures, the next below are sedimentary marine strata or Millstone grits, and these rest on marine limestones and shales constituting the Mountain or Carboniferous Limestone series.

The Coal-measures consist of alternations of coal-seams resting on clay or siliceous deposits, and which are covered by gravels, shales, or ironstones, and they are of freshwater, brackish-water, and sometimes of marine origin.

A A

The Millstone grits were the wear and tear of arenaceous rocks and granites, and the mountain limestones and shales beneath, were marine deposits composed of the remains of Foraminifera, Testacea, Crinoidea, Corals, &c.

In the south-western part of England, in Somersetshire and South Wales, the three divisions of the Carboniferous formation

These divisions are indicated upon the diagram, fig. 84, p. 99; but the position of the Lower limestone shale is at the base of the limestone.

General Notice of the Divisions.-The coal-measures of the North of England differ, to a certain extent, from those of the south-west; but a typical series would include the following strata. Top. 1. Red and grey sandstones, clays, and sometimes breccias, with occasional coal-seams and streaks of coal and Spirorbis limestone with Cythere inflata. 2. Middle coals, yellow sandstones, clays, and shales, with numerous workable coalseams resting on fire-clays: fossils, Anthracosia, Anthracomya, Beyrichia, Estheria, Spirorbis. 3. Lower beds, gannister beds, flagstones, shales and thin coals, with hard siliceous layers beneath the coal-seams. Flagstones intercalated. Fossils, Aviculopecten, Lingula, Goniatites, Orthoceras. Bone-bed, with fish and Labyrinthodonts.

In Scotland the equivalents of the uppermost beds above mentioned, are probably a red sandstone group without coals, overlying workable (flat) coals; and in the North-west of England these beds are barren here and there, as at Wigan; but at Manchester they are important and coal bearing. At Burnley, on the other hand, the beds are absent.

The Millstone grit, well seen in South Wales, is grandly developed beneath some Coal-measures, and feebly beneath others, or it may be wanting. For along a line drawn from Shropshire through South Staffordshire, Leicestershire, to the Wash, a ridge of Paleozoic rocks exists at a greater or less depth, from or at the surface, on which little or usually no marine accumulations

could occur. Hence the coal-measures at Coalbrookdale, South Staffordshire, rest upon Silurian rock with a very little gannister grit (or none) intervening.

This ridge of old rocks, or 'central barrier,' was a Carboniferous land surface, and the grits collected on either flank, increasing however in thickness vastly far away to the north and west, and attaining a thickness of 9,000 feet in North Staffordshire, 12,130 feet in South Lancashire, and 18,700 feet in North Lancashire.

The thickness of the grits at the edge of the Staffordshire coal-field is only 200 feet, and it is 3,000 feet in Western Yorkshire.

The grits vary greatly in their lithology. Some are very rough and massive, others are fine-bedded micaceous sandstones and flags, whilst the bulk are jointed or are strata of varying thicknesses, and with the grains very visible to the eye. All are siliceous and felspathic, and the grains are often united by a felspathic matrix. The area whence the grits come, carried by marine currents, was in the north-west. Thin coal-seams and coal plants are found in some places in the grits, and sometimes a marine fauna exists, which contains fossils of the same species as those found in the lower strata called Carboniferous limestone.

The grits are divided into the Rough Rock, or first grit, which underlies the lower Coal-measures; the Flag Rock or Haslingdon Flags, or second grit, with shales and thin coal; the third grit of gritstone, flagstone shale, and thin coals, with marine fossils; the Kinderscout grit, or fourth grit: this forms the Peak in Derbyshire.

In Scotland the Moor rock, with thin seams of coal, is the equivalent of the English grits, and its very moderate thickness diminishes in Ayrshire, where it consists of a few beds of sandstone at the base of the coal-measures.

Carboniferous Limestone Series.-In Yorkshire there is a downward continuation of sandstones and shales, resembling those of the Millstone grits, with intercalated limestones, some of which are thick and crowded with Encrinites. Phillips called these the Yoredale series, and they attain the thickness of from 800 to 1,000 feet in Yoredale. The genera of marine fossils which are found in these strata are Nautilus, Orthoceras, Phragmoceras, Goniatites, Euomphalus, Bellerophon, Cerithium, Spirifera, Phillipsia, Zaphrentis, &c., and these are common in the underlying Carboniferous limestone. Beds of thin coals occur in the lower Yoredale strata. These strata are not found in the Centre and South of England, where the true Mountain or Carboniferous limestone exists.