3U8                                                 SILURIA.                                     [Chap. XIII.
 

CHAPTER XIII.
PERMIAN ROCKS.

CHANGES   OF  THE  FORMER  SURFACE.----ORIGIN OF THE TERM   * PERMIAN '  AS APPLIED TO THE

HIGHEST GROUP OF PALEOZOIC DEPOSITS.—THE PERMIAN ROCKS OF RUSSIA, GERMANY, AND
BRITAIN.—THE ORGANIC REMAINS OF THE GROUP.

Ix the two previous Chapters, slight allusions only have been made to ig¬
neous or volcanic materials ejected and spread out on the sea-bottom con¬
temporaneously with the ordinary sedimentary deposits ; for during the
Devonian and Carboniferous eras such eruptions were by no means so
abundant in the British area as when the Lower SUurian rocks were
accumulated.    (See pp. 76 &c.)

The great Upper Coal-fields considered in the previous Chapter were
probably, in regions hke Britain and America, evolved under conditions
which geologists would consider comparatively quiescent. This is supposed
to have been particularly the case with those coal-beds which were formed
either by continuous depressions of low lands beneath the waters or by
alternations of subaqueous and terrestrial surfaces. The close, however, of
that period was speciaUy marked by ruptures of the crust of the earth,
which, from the physical evidences placed before us, must have extended
over very distant regions. Whatever may have been the previous changes,
it was then that the coal-strata and their antecedent formations were very
generaUy broken up, by upheavals, into separate troughs and basins, dis¬
torted by numberless powerful dislocations. The order of ancient sedi¬
mentary succession was thus very widely, though not universaUy, inter¬
rupted ; and aU the strata previously spoken of were so disturbed as to
produce a prevalent break or discordance between the Carboniferous de¬
posits and those which succeeded to them»

This disturbance, however, was not general, since there are exceptional
tracts in which the Carboniferous and overlying Permian deposits are in
apparently conformable relation to each other.

The general effect of the great disseverment aUuded to, in determining a
former outline of the earth, is obvious ; for, whilst the SUurian, Devonian,
and Carboniferous rocks were at that period so heaved up as to constitute
portions of mountain-chains, the strata which we are now considering have
been for the most part spread out in lesser elevations, constituting coun¬
tries with a lower level. Yet, notwithstanding these physical changes,
the animals and plants of the Permian era, though chiefly of new spe¬
cies, are genericaUy connected with those of the preceding or Carboni-