and M. Mourlon concludes that the Tangier promontory consists of Eocene beds resting on Cretaceous.
The eastern half of the northern promontory, including Tetuan and Apes’ Hill facing Gibraltar, consists of beds of a different character, for the most part of a hard metamorphic limestone, in which dip and strike are very obscure: these may be a southern extension of the Gibraltar limestone; but I had no opportunity of tracing the connection to Tetuan.
The late James Smith, of Jordan Hill (in ‘Journal of Geological Society,’ vol. ii. p. 41), mentions the occurrence of casts of Terebratula fimbriata and T. concinna, belonging to the Lower Oolite, in the Gibraltar limestone. M. Coquand also assigns to the Jurassic period the beds in the neighbourhood of Tetuan, and divides them into four stages, characterised respectively by marls, dolomites, a calcareous sandstone with the odour of petroleum, and a lithographic limestone containing siliceous concretions. I am of opinion that the Tetuan series, ranging with the Gibraltar limestone, and probably extending far to the south, is separated from the more recent Cretaceous series to the west and north-west by a great north and south fault, which divides nearly equally the Tangier promontory. M. Mourlon, referring to some specimens of shelly limestone in the Brussels Museum, collected near the river Mhellah in the district of Ouled Eissa, between Fez and Tetuan, resembling the Muschelkalk in aspect, and associated with beds resembling those at Tetuan, considers that they may also be of Jurassic age.
The Tetuan limestone has given rise to enormous beds of brecciated tufa, on terraces of which the city is built. The flow seems to have taken place from the hills to the north-west of the city, and has produced beds of a collective thickness of 60 or 70 feet. This is evidently true tufa, due to aqueous deposition, and is of a different character from the great calcareous sheet, to which I shall have occasion further to refer, which shrouds over the entire plain of Marocco.
Respecting the Mediterranean coast-line of Barbary, I will not add much to a paper read before the British Association at Liverpool, in which I remarked on the singular absence of coast-cliffs of any height. The undulating contour of the land-surface extends down to the water’s edge, a continuation of the form of the bottom of the straits without the intervention of cliff-escarpments, from which I surmised that the present sea-level and coast-line of the straits had not been of long duration.
Of frequent changes of level on the Barbary coast there is abundant evidence. The more recent seem to be, first, an elevation of from 60 to 70 feet along the entire coast, implied by the existence of concrete sand-cliffs with recent shells exactly similar to the raised beaches of Devon and Cornwall. These occur in Tangier Bay to a height of 40 feet, resting on the upturned edges of nearly vertical mesozoic beds; to the south of Cape Spartel, as a long cliff nearly 50 feet high; as low shoals near Casa Blanca; as a compact cliff about 50 feet high at Saffi, and as a coast-cliff and islands at Mogador, where the concrete sand-beds attain a height of 60 or 70 feet above the sea-level. It seems probable that this elevation of coast-line was coincident with a similar rise, implied by the existence of concrete sand-cliffs, all along the Spanish and Portuguese coasts, viz. on the eastern face of Gibraltar, where stratified raised beaches are seen cropping up at a considerable height from under the great mass of drift-sand in Catalan Bay; at Cadiz, as low cliffs 40 to 50 feet high, forming a hard coarse freestone of which the city is built; and also at the Rock of Lisbon, where, at a height of from 150 to 180 feet, isolated fragments of stratified concrete sandstone are seen clinging to the sea-escarpment of the older rocks.
The great range of latitude included in this simultaneous coast-rise suggests the probability that the elevation of similar coast-beds in Devon and Cornwall may pertain to the same movement.
Judging from the evidence afforded by the coast near Mogador, a subsequent submergence appears to be taking place. The island is probably diminishing in bulk; and, from observations made by M. Beaumier, the French Consul, it appears to have been reduced about one-fourth in area in twenty years; but whether from denudation or subsidence is not clear. The sea is, however, sensibly encroaching, as an old Portuguese fort and some Moorish buildings are now environed with sand and salt-marsh close to the sea, in a position where they would not have been built. This submergence of the coast at Mogador may perhaps be contemporaneous with the subsidence at Benghazi, Barbary, described by Mr. G. B. Stacey in the twenty-third volume of the ‘Quarterly Journal of the Geological Society.’ The general absence of cliffs characterises nearly the whole of the Barbary coast. A few low cliffs occur at scattered intervals west of Tangier; but from Cape Spartel to Cape Cantin a low monotonous coast shelves under the waters of the Atlantic, and not a cliff is to be seen, save an occasional raised beach. After rounding Cape Cantin the coast trends nearly north and south; and here the first good coast-section presents itself as a vertical cliff nearly 200 feet high (fig. 1), consisting of nearly level stratified alternations of grey and reddish marl, and fine-grained sandstone with beds of argillaceous carbonate of iron resembling the cement-stone of the Kimmeridge clay.
At a distance the cliff has a massive rocky aspect due to the vertical infiltration of tufaceous seams, which support the softer beds and stand out in prominent masses. The cliffs continue southwards to Saffi, where I obtained a small series of fossils from the section represented in fig. 1, amongst which Mr. Etheridge has determined Exogyra conica, Ostrea Leymerii, and 0. Boussingaulti. He considers the beds to be of Neocomian age. The hard band c is almost entirely made up of Exogyra conica.
I am indebted to the late Mr. Carstensen, H.B.M. Vice-consul at Mogador, for a specimen of Ostrea Leymerii, brought