le region, covering Devonshire and Cornwall, the
Ardennes, the northern part of the lower Rhenish mountains, and the
upper Harz to the Polish Mittelgebirge; here we find evidence of a
shallow sea, clastic deposits and a sublittoral fauna. (3) A southern
region reaching from Brittany to the south of the Rhenish mountains,
lower Harz, Thuringia and Bohemia; here was a deeper sea with a more
pelagic fauna. It must be borne in mind that the above-mentioned regions
are intended to refer to the time when the extension of the Devonian sea
was near its maximum. In the case of North America it has been shown
that in early and middle Devonian time more or less distinct faunas
invaded the continent from five different centres, viz. the Helderberg,
the Oriskany, the Onondaga, the southern Hamilton and the north-western
Hamilton; these reached the interior approximately in the order given.

Towards the close of the period, when the various local faunas had
mingled one with another and a more generalized life assemblage had been
evolved, we find many forms with a very wide range, indicating great
uniformity of conditions. Thus we find identical species of brachiopods
inhabiting the Devonian seas of England, France, Belgium, Germany,
Russia, southern Asia and China; such are, _Hypothyris_ (_Rhynchonella_)
_cuboides_, _Spirifer disjunctus_ and others. The fauna of the
_Calceola_ shales can be traced from western Europe to Armenia and
Siberia; the _Stringocephalus_ limestones are represented in Belgium,
England, the Urals and Canada; and the (_Gephyroceras_) _intumescens_
shales are found in western Europe and in Manitoba.

The Devonian period was one of comparative quietude; no violent crustal
movements seem to have taken place, and while some changes of level
occurred towards its close in Great Britain, Bohemia and Russia,
generally the passage from Devonian to Carboniferous conditions was
quite gradual. In later periods these rocks have suffered considerable
movement and metamorphism, as in the Harz, Devonshire and Cornwall, and
in the Belgian coalfields, where they have frequently been thrust over
the younger Carboniferous rocks. Volcanic activity was fairly
widespread, particularly during the middle portion of the period. In the
Old Red rocks of Scotland there is a great thickness (6000 ft.) of
igneous rocks, including diabases and andesitic lavas with agglomerates
and tuffs. In Devonshire diabases and tuffs are found in the middle