- 
Parr II. Seor. iii, (1) §1.] DEVONIAN. | 695 
Red Sandstone, which would thus become the sole representative in 
Kurope of the interval between Silurian and Carboniferous time. 
In the following descriptions an account will first be given of the 
Devonian type and then of the Old Red Sandstone. 
I. DEVONIAN TYPE. 
$1. General Characters. 
Rocoxs.—Throughout Central and Western Europe the Devonian 
system presents a remarkable persistence of petrographical characters, 
indicating probably the prevalence of the same kind of physical 
conditions over the area during the period when the rocks were 
accumulated. ‘The lower division consists mainly of sandstones, 
grits, and greywackes. ‘These rocks attain a great development on 
the Rhine, where they form the material through which the 
picturesque gorges of the river have been eroded. In the central 
zone limestones predominate, some of them crowded with the corals 
and molluscs of the clearer water in which they were laid down. 
The upper series is more variable: being in some tracts composed 
of sandstones and shales, in others of shales and limestones, but 
everywhere presenting a more shaly thin-bedded aspect than the 
subdivisions beneath it. Considerable masses of diabase, tuff, and 
other associated rocks are intercalated in the Devonian system of 
Germany. Asa rule the rocks have been subjected to more or less 
disturbance, having been thrown into plications, and sometimes, as in 
Cornwall and Devon, having even undergone extensive cleavage. In 
some localities also they have been metamorphosed into schists, 
quartzites, &c., and have been invaded by large masses of granite and 
other eruptive rocks. 
Among the economic products the most important in Europe are 
the ores of iron, lead, tin, copper, &ec., which occur in veins or 
lenticular masses through the Devonian rocks (Devon and Cornwall, 
Harz, &.). In North America the Devonian rocks of Pennsylvania 
contain bands of “‘ sand-rock ” charged with petroleum. 
Lirze.—An abundant cryptogamic flora covered the land during 
- the ages that succeeded the Silurian period. As the remains of this 
vegetation are chiefly preserved in the Old Red Sandstone facies of 
deposits, it is described at p. 706. The fauna of the Devonian 
rocks is unequivocally marine. Among the more lowly forms of 
life are some the true zoological grade of which has been the subject 
of much uncertainty. Of these, the fossil known as Calceola sanda- 
lina (Fig. 330) has been successively described as a lamellibranch, a 
1 See his papers in Journ. Roy. Geol. Soc. Ireland (1865), i. pt. 1, new ser., and 
Quart. Journ. Geol. Soc. xxii. (1866), and his pamphlet on Additional Notes on Rocks of 
North Devon, &c., 1867. The “ Devonian question,” as it has been called, has evoked a 
large number of papers, of which, besides those quoted in subsequent pages, the fol- 
lowing may be enumerated :—Prof. Hull, Q. J. Geol. Soc. xxxv, (1879), p. 699; Xxxvi. 
(1880), p. 255. A, Champernowne, Geol. Mag. v. 2nd Ser. (1878), p. 193; vi. (1879), 
p- 125; viii. (1881), p. 410. ‘The general verdict has been adverse to the explanation of 
the structure of North Devon proposed by Mr. Jukes. 
