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 by insensible gradations, and contain a considerable number of fossils in common.

The lowest of these consists of alternations of limestones, sandstones, and marls, yielding a large series of fossils, by means of which it is referred without doubt to the Urgonien. Its thickness is about 500 feet ; and it rests indifferently (the Lower Neocomian being absent) on all the older rocks. In the Utrillas basin this division contains only jet, but in other districts it furnishes beds of coal. It is in these that the mines of Santa Barbara and la Fuen Gargallo are worked.

The second series, consisting of ferruginous sandstones and limestones alternating with sandy clays, is that which contains the same fossils as the Marine Band of Punfield. These beds, although their fauna presents some peculiarities, are doubtless to be referred to the highest portion of the Middle Neocomian. At Utrillas, where they attain a thickness of 530 feet, they contain ten beds of coal, lignite, or jet, which are extensively worked. It is these beds which constitute the Calcaire a Trigonies of M. de Verneuil. The fauna of these beds seems to be especially characterized by the presence in great abundance of Gasteropods of a new genus, which has already unfortunately received four names (Cerithium, Omphalia, Cassiope, and Vicarya). No less than six species of this genus have been described from Utrillas, three of which occur at Punfield, and one of them in the " Rhodanien " of Switzerland. It is remarkable that there is scarcely a single fossil found in the Marine bed of Punfield which does not also occur in these Spanish beds.

The third and highest of these series of Spanish rocks consists of variegated and mottled clays and sands of bright colours (crimson, grey, green, violet, and white), which greatly resemble the Keuper, and were, indeed, long mistaken for it. They are probably in great part of freshwater origin, though a few marine shells have been found in them, which enable us to refer the series to the Upper Neocomian. Their lower portion consists of dark-coloured clays with a pyritous combustible mineral, formerly used for the manufacture of alum. This series, which is 600 feet thick, contains beds of lignite, which are worked in many places. It is overlain by strata representing the Gault and other members of the Cretaceous.

These coal-basins of Eastern Spain have been estimated as being capable of supplying the whole of the peninsula for more than 200 years.

VIII. Conclusion.

The grounds on which I have ventured to suggest that the strata, the nature and relations of which I have endeavoured to illustrate in the preceding pages, are worthy to rank as an independent formation* are as follows : —

with two very different significations — either to indicate great groups of strata like the "Silurian" or "Jurassic," or for smaller divisions, like the "Ludlow series," or the "Great Oolite." It is with the latter meaning only I have
 * The term "formation" is unfortunately employed by English geologists