310 • Geological Society. 



they lie is inclined at a considerable angle. The narrow valley of 

 Alcantara, close to Lisbon, is the line of a considerable fault, the 

 strata dipping in opposite directions from the valley, or 15° towards 

 the west, and 10° towards the east. Another anteclinal line inter- 

 sects the upper part of this valley ; and at the point where the two 

 disturbances cross, considerable derangement of the strata is produced. 

 In one quarry Mr. Sharpe noticed eight small faults, and the walls 

 of the rocks on each side of the fissures had a beautiful polish. 

 Though the author has adopted the term Hippurite limestone for 

 this deposit, yet he did not discover any remains of that genus, but 

 great abundance of Spherulites, some of them probably of known 

 species, and other fossils of the family of Rudista. He obtained 

 also a considerable number of shells, including Exogyra flabellala, 

 Pecten quadricostatus and Pecten striato-costatus. 



(e.) Red Sandstone. — This formation consists of various sands, 

 sandstones, marls, and limestone, which are grouped by Mr. Sharpe 

 in the following manner : 



Upper Division. — Ferruginous sands, sandstones, and coloured 

 marls. 



Middle Division. — Calcareous sandstones and coarse limestones. 

 Lowest Division. — Coarse sands, sandstones, and grits. 

 The extent of country, composed of this formation, is very con- 

 siderable. North of the Tagus, the red sandstone covers the greater 

 portion of the area to the westward of the tertiary strata and Hip- 

 purite limestone, the only tract belonging to other deposits being 

 the hills at Cintra, and the lower ridges immediately surrounding 

 them. A denuded strip of sandstone is also exposed between Loures 

 and Cape Sinchette. South of the Tagus, the red sandstone forms 

 a tract of variable breadth, extending from Palmella to the coast, a 

 little north of Cape Espichel. The beds of this formation are greatly 

 affected by faults and vary much in the angle of inclination, but the 

 prevailing dip is towards the south-east throughout the districts on 

 the Lisbon side of the Tagus. In the tract between Palmella and 

 the coast, the strata have also been disturbed by considerable faults, 

 but their usual dip is north, or north-west, at a high angle. Near 

 Lisbon, the connexion of the red sandstone with the subjacent for- 

 mations is not often exposed. North of Cintra the sandstone rests 

 almost horizontally upon inclined strata of Espichel limestone, 

 shale, San Pedro limestone and granite. South of the Cintra hills, 

 it reposes very irregularly upon the Espichel limestone : and south 

 of the Tagus, with every degree of want of conformity, upon the 

 limestone of the Serra d'Arrabida (Espichel limestone) ; and in a 

 great variety of positions upon the lofty peaks of the older red con- 

 glomerate of the Cavoens and the Serra de San Luiz near St. Ubes. 

 Lignite occurs in several places, and in sufficient quantities to have 

 led to unsuccessful researches for coal. Sulphur also thickly en- 

 crusts some of the sandstone strata ; and gypsum has been worked 

 near Santa Anna, south of the Tagus. Mr. Sharpe is of opinion, 

 that the tepid springs of Estoril,near Cascaes, may derive their virtues 

 from the sulphureous strata ; and that the hot springs of Caldas 

 da Rainha may owe their sulphureous qualities to similar strata. 





