TRANSACTIONS OF THE SECTIONS. 111 
tander and Biscay, seems to correspond with the upper greensand, but not with the 
Neocomian or lower greensand. M. de Verneuil speaks only of what is known in 
the present state of the geology of Spain, for it is probable that future researches 
will indicate the existence of the Neocomian formation in the peninsula. 
The above-mentioned upper member of the cretaceous group is widely spread 
over Spain as well as over Portugal, where it has been described by Mr. Sharpe. 
From the province of Santander it extends to the Asturias near Oviedo, and to Bonor 
and Sabero (Leon). The same hippuritic limestone is known in the neighbourhood 
of Burgos, near Tamajon, in the province of Guadalajarra and not far from Segovia. 
One of the most common fossils of these beds is the Exogyra flabellata known at 
Teruel, Titaguas, Tamajon, Burgos, &c. 
Above the chalk, and, having, apparently been submitted to the same disturbances, 
lie the nummulitic rocks, which most geologists now consider to be true eocene. 
They are very well exposed at Columbres (province of Santander). With Num- 
mulites of all size, some being gigantic, occur the Conoclypeus conoideus and the 
Serpula spirulea. Much uncertainty still reigns concerning the nummulitic tracts in 
Spain, for the double reason that Orbitolites have been sometimes mistaken for 
Nummulites, and that in other cases true Nummulites have been confounded and 
mapped with cretaceous rocks upon which they lie, but into which they never descend ; 
thus according with the position they have been shown to occupy in the Alps, Apen- 
nines and Carpathians, by Sir Roderick Murchison. - Among other places where 
Nummulites are known, the French geologist quotes the neighbourhoods of Malaga, 
Gualchos, Motril, Tarragona, Geronse, Olot, &c. At Malaga a great discordance 
may be observed between the nummulitic limestone and the miocene deposits, the 
first being highly contorted and the second slightly elevated. Judging from the few 
fossils collected by M. Ezquerra del Bayo, the lignites of Utrillas in Arragon must 
belong, like those of Entrevernes in Savoy, to the nummulitic period. 
Tertiary rocks.—These rocks cover vast areas in Spain. Being generally hori- 
zontal and extending in vast plains, they contrast strongly with the secondary and 
nummulitic beds, which are always contorted and form undulating or mountainous 
countries. ΑἹ] the great valleys of the Ebro, the Douro, the Tagus, the Guadiana 
and the Guadalquivir, have been bottoms of seas or extensive lakes. The freshwater 
deposits cover a larger area than the marine ones, extending over Old and New 
Castile from the Cantabrian chain to the Guadarrama, and from the Guadarrama to 
the Sierra Morena through the great plains of the Mancha. In some places these 
deposits reach the altitude of 2500 feet ; thus proving how great elevation Spain has 
suffered even in recent times; recent in effect, if we judge by the freshwater fossil 
shells which are said to be identical with those living now, and by the bones of great 
mammoths discovered in the Cerro San Isidro near Madrid. Most of the marine 
deposits, and especially those of the basin of the Guadalquivir, are miocene, and upon 
them lie here and there some small pliocene, or newer pliocene deposits, formed on 
the littoral shore and composed of pebbles and fragments of an Ostrea resembling 
the living species. Cadiz is built upon such rocks, which are also well-known in 
Algeria,. The Mediterranean coast presents many instances of smal! miocene de- 
posits, some of which have been disturbed and support horizontal newer beds. 
It was probably in the most recent of these periods that the extinct volcanos of 
the Peninsula broke out. Three foci of eruption are known; one at the cape of 
Gata, the other in the neighbourhood of Ciudad Real, and the third near Olot in 
Catalonia. 
The geology of Spain is not sufficiently advanced to attempt a classification of its 
mountains considered with respect to their periods of elevation. It may, however, 
be said, that the Sierra Morena, though a low range, is the most ancient; for on 
both its sides the tertiary strata in contact with the old rocks are horizontal. Near 
Cordova, for example, the miocene beds with the huge Clypeaster altus are to be seen 
in that position, and on the northern side at Santa Cruz de Mudela horizontal bands 
of freshwater limestone loaded with Helix, lie upon highly inclined, trilobite Silurian 
schists. More recent movements have taken place in the Guadarrama; since at the 
southern foot of that high range, and on the road from Madrid to Burgos, the same 
freshwater limestone is slightly elevated. In the Pyrenees, as well as in the moun- 
tains which rise in the most southern part of Spain, the subsoil has. been tormented 
