Sullivan & O'Eeilly — On Dolomite Bed of North of Spain. 227 
"bearing upon the Santander rocks, we must first briefly state the posi- 
tion in which we left the question of the stratigraphical succession of 
the rocks of Santander, when we published our paper on the minera- 
logy and geology of that province in 1863>' 
M. De Yerneuil, who examined part of the country lying north of 
the Cantabrian extension of the Pyrenees, in 1849, came to the con- 
clusion that one of the sub-chains in the Montana or province of 
Santander, the Dobra Eange, was carboniferous, and, consequently, 
connected with the large developments of that formation stated to exist 
further west in the Asturias. Against the carboniferous limestone of 
the Monte Dobra he found resting, as he believed unconformably, a 
system of sandstones, conglomerates, and blue argillaceous limestones 
belonging to the lias. Subsequent observations led him to regard the 
whole as forming part of a band of jurassic rocks, about nine miles 
wide from north to south, and thirty-six miles long from east to west, 
stretching in length from La Cabada to Fuente de Nansa. This 
jurassic band he believed to rest towards the west, or rather south- 
west, on triassic rocks — a crescent- shaped island of which it enclosed 
to the south of Yargas — and to pass under cretaceous rocks, except when 
in contact with the trias. 
In our paper just referred to we not only came independently to 
the conclusion that the Dobra Eange was jurassic, but that the rocks 
of that formation, instead of ending at Euente de UTansa, as M. de Yer- 
neuil thought, extended across the Eiver Deva ; in other words, the 
great limestone masses of the Liebana and of the south-east of the 
Asturias were also jurassic. If this be so, the limestone in question 
forms some of the highest peaks of the Cantabrian chain, the Picos de 
Europa, which had hitherto been universally considered to belong to 
the carboniferous period. 
We also showed that in the district near the coast hitherto de- 
scribed as cretaceous, denudation had laid bare in the valleys rocks of 
a jurassic character. Among these is a great bed of dolomite, in some 
places 120 metres thick, which we were the first to describe, and to 
show its connexion with the mineral deposits of the locality. We 
considered this bed as the top of the jurassic series, and suggested 
that it extended under all the cretaceous rocks of theJ^orth of Spain, 
which rest upon jurassic ones. 
The relation of the dolomite bed with the other rocks, and its 
connexion with deposits of ores, was illustrated in our paper, by 
several sections, one of which we have given in the annexed plate, 
(see PL xviii.. Science). The section here selected is that passing 
from north to south through the valleys of Comillas and Udias. 
As the scale of this section is very small, and can only show, at most, 
the general relations of the beds, we have added an enlarged section of 
* " Atlantis," vol. iv., p. 319 ; and " Notes on the Geology and Mineralogy of 
the Spanish Provinces of Santander and Madrid." London: 8vo; 1863. 
