256 The American Naturalist. [April, 
Sketch of the Geology of Spain. — The Reseiia Geogra- 
phica y Estadistica of Spain, issued during the past year, con- 
tains an introductory article upon the geology of the peninsula 
by D. Juan Bisso. During the Cambrian age the surface of 
Spain presented a multitude of isles and islets, composed in 
great portion of igneous rocks, but containing also stratified 
crystalline strata. The principal island, already quite extensive, 
occupied the greater part of Galicia, the north of Portugal and 
small portions of the present provinces of Caceres, Salamanca, 
and Zamora. Another isle occupied the eastern portion of the 
present Castilian provinces of Avila, Segovia, and Toledo. A 
great number of islets were strewn in what is now the southern 
part of Portugal, Estremadura, and north-western Andalucia. 
Toward the North arose some points in the line which event- 
ually became the northern Cordillera. Later on, at the close 
of the Cambrian, the important slate deposits of the Pyrenees 
arose above sea-level, together with portions of Estremadura, 
and of the southern Andalucian mountains. 
Throughout the Silurian and Devonian periods the main 
island increased considerably, so that at the commencement of 
the Carboniferous, it occupied all Galicia, the west of Asturias, 
and the provinces of Leon and Zamora, its southern line run- 
ning by Ledesma, Salamanca, Sepulveda, and Siguenza, and 
then turning south in an irregular curve so as to embrace, in the 
same mass, the sites of Madrid, Toledo, Cuidad Real and 
Alcarez. Its most southerly extension reached the Sierra 
Morena, and its western coast extended to Oporto. At the 
same period a great part of the Pyrenees had emerged, as well 
as many islands, in Catalonia, between Burgos and Soria, in 
western Aragon and eastern Castile. In the south parts of the 
Sierra Nevada and the extreme south-east of the peninsula had 
appeared. Permian strata have not been, with certainty, met 
with in Spain. 
In the Triassic period the principal mass already extended 
much to the southeast, and in Portugal and Huelva had almost 
reached its present limits, comprehending Seville and Cordova 
in its southern extension. In the northeastern it occupied all 
of Oviedo and Leon, Zamora and Salamanca, great part of the 
provinces of Valencia and Santander. The Pyrenees formed a 
zone as now ; almost all the southeastern islands united forming 
a tract occupying great part of the present provinces of Murcia, 
Almeria, Granada and Malaga. 
The Jurassic seas must have occupied but a small extent, 
since at the conclusion of the Triassic, the greater part of 
