418 
SILURIA. 
[Chap. XVII. 
last-mentioned city by the late Mr. S. P. Pratt, who explored several tracts in 
Spain *. 
Devonian Rocks in Spain. — Devonian rocks are developed in the Sierra Mo- 
rena north and south of Ahnaden, and occur in several repetitions troughed by 
Lower Silurian rocks, the fossils lying generally in sandstones or in small bands 
of impure limestone. The most characteristic species are Productus subacu- 
leatus, Leptaena Dutertrii, Spirifer Verneuilii, Sp. Archiaci, Sp. Bouchardi, 
Orthis striatula, Atrypa reticularis, A. Orbignyana, A. concentrica, Phacops 
latifrons, &c. All these but one (A. Orbignyana) are common fossils at Bou- 
logne ; and there are many others which are well known in French and Ger- 
man localities, besides some species peculiar to Spain. In the southern parts 
of Cu^nca, near Hinarejos, de Verneuil and Collomb also detected deposits con- 
taining Lower-Devonian fossils, including the Spirifer macropterus of the 
Rhine t ; and in 1852 the equivalent deposits were traced at the eastern ex- 
tremity of the Guadarama range between Atienza and Siguenza, by de Verneuil 
and de Loriere. 
Whilst the western parts of the Sierra Cantabrica, extending from the high- 
road from Leon to Oviedo, are now known to be composed of quartzose and 
schistose strata of Silurian age, Casiano de Prado having detected Graptolites in 
them, the middle part of this chain presents a very rich development of Lower- 
Devonian deposits %. These rocks consist of red sandstone, shale, and grey lime- 
stones, which, owing to powerful dislocations, assume bold and peaked forms, 
visible at great distances from the plains of Castile. They are as prolific in 
mineral wealth as in organic remains, the iron of Mieres and Sabero being ex- 
tracted from them §. Thanks to the labours of Schultz, Casiano de Prado, 
Paillette, de Verneuil, and d'Archiac, the successive formations of these coun- 
tries are now becoming much better known. 
Carboniferous Rocks of Spain. — Proceeding to the east, the Devonian rocks of 
the Sierra Cantabrica are succeeded in the Asturias by the richest Coal-field in 
Spain. Its lower beds consist of massive limestones, having so much resem- 
blance to the Devonian rocks on which they lie, that, except for their respective 
organic remains, they could with difficulty be separated. The fossils, however, 
are decisive of the superior rock ; for among them are several well-known 
British species of Productus, such as P. semireticulatus, together with Spirifer 
Mosquensis, and even Fusulina cylindrica, the characteristic Foraminifer of the 
Carboniferous Limestone of Russia. Above these masses, beds of coal first 
begin to alternate with other and smaller courses of limestone ; and therefore in 
Spain as in Russia, and in the Lower Coal-beds of Scotland, the carbonaceous 
portion is subordinate to the Carboniferous or Mountain Limestone. Then 
follow conglomerates and sandstone, with fossil Plants, said to have a thickness 
of 10,000 feet, and which, probably representing the Millstone-grit of Britain, 
are copiously charged with coal, about eighty beds of it having been recognized, 
in strata for the most part vertical. 
* See Quart. Journ. Geol. Lond. vol. viii. p. 270. quelqu'unes des roches de9 Asturies, et le3 fos- 
t M. Jacquot quotes also the Leptaena ATur- siles qu'elles contiennent,' par Paillette, de Ver- 
chisoni in his ' Esquisse Ge'ologique de la Serrania neuil, et d'Archiac, Bull. Soc. Geol. Fr., 2nd series, 
de Cuenca' (1866). vol. ii. p. 439. 3rd. ' Sur les Environs de Sabero 
I M. de Verneuil has identified nearly 80 De- (Leon),' par Casiano de Prado et de Verneuil, 
vonian species from Sabero in Leon and from Bull. Soc. Geol. Fr. 2nd ser. vol. vii. p. 137. 
Perrones and Aviles in the Asturias, which ought, § Though the coal of Sabero is apparently in- 
he says, to be places of pilgrimage for all collec- eluded among the Devonian rocks, M. Casiano de 
tors. Of the works on this region, see, 1st, ' Re- Prado thinks that this appearance may be due to 
sena geognostica del principado de las Asturias, inversion and folding of the various strata; so 
Vista geolog. sobre Cantabria,' by G. Schultz, much has this Palaeozoic tract been convulsed. 
Insp. Gen. de Minas. 2nd, ' Recherches sur 
