phical Society).
Thomas Davidson.
(37) 'Graptolites of the Quebec Group.' James Hall.
(38) 'Monograph of the British Graptolitidae.' Nicholson.
(39) 'Monographs on the Trilobites. Pteropods, Cephalopods,
Graptolites,' &c. Extracted from the 'Systeme Silurien du Centre
de la Boheme.' Barrande.
(40) 'Polypiers Fossiles des Terrains Paleozoiques,' and 'Monograph
of the British Corals' (Palaeontographical Society). Milne
Edwards and Jules Haime.

CHAPTER XI.

THE DEVONIAN AND OLD RED SANDSTONE PERIOD.

Between the summit of the Ludlow formation and the strata which
are universally admitted to belong to the Carboniferous series
is a great system of deposits, to which the name of "Old Red
Sandstone" was originally applied, to distinguish them from certain
arenaceous strata which lie above the coal ("New Red Sandstone").
The Old Red Sandstone, properly so called, was originally described
and investigated as occurring in Scotland and in South Wales and
its borders; and similar strata occur in the south of Ireland.
Subsequently it was discovered that sediments of a different mineral
nature, and containing different organic remains, intervened
between the Silurian and the Carboniferous rocks on the continent
of Europe, and strata with similar palaeontological characters to
these were found occupying a considerable area in Devonshire.
The name of "Devonian" was applied to these deposits; and this
title, by common usage, has come to be regarded as synonymous
with the name of "Old Red Sandstone." Lastly, a magnificent series
of deposits, containing marine fossils, and undoubtedly equivalent
to the true "Devonian" of Devonshire, Rhenish Prussia, Belgium,
and France, is found to intervene in North America between the
summit of the Silurian and the base of the Carboniferous rocks.

Much difficulty has been felt in correlating the true "Devonian
Rocks" with the typical "Old Red Sandstone"--this difficulty arising
from the fact that though both formations are fossiliferous, the
peculiar fossils of each have only been rarely and partially found
associated together. The characteristic crustaceans and many of the
characteristic fishes of the Old Red are wanting in the Devonian;
whilst the corals and marine shells of the latter do not occur in
the former. It is impossible here to enter into any discussion
as to the merits of the controversy to which this difficulty
has given origin. No one, however, can