Page:Quarterly Journal of the Geological Society of London, vol. 35.djvu/614

518 denuded at different points, and is being now rapidly broken up by aqueous and atmospheric agencies. In its structure the following characters seem constant. (1) The upper portion is much broken and intersected by cracks and fissures, forming a rubbly white limestone, which forms the surface rock of the Benjemma plateau. (2) The above passes imperceptibly into a yellowish white rock, which is soft and forms almost a calcareous sandstone easily acted on by the weather, as is well seen on the cliffs west of Città Vecchia. (3) The last gradually merges into a red limestone of considerable durability and composed more or less of Corallines, Nullipores, Polyzoa, &c. It forms a prominent feature in the cliffs of Gozo and south-western aspects of Malta.

The invertebrate fossils of the Upper Limestone are numerous; but it is markedly poor in vertebrata as compared with the underlying formations.

The following Brachiopoda collected by me in the Upper Limestone have been determined by Mr. Davidson, F.R.S.,—Terebratula sinuosa, Megerlia truncata, Argiope decollata, Rhynchonella bipartita.

The Mollusca are represented by at least five species of Pecten—to wit, P. Pandora, P. burdigalensis, P. Beudanti, P. scabellus, P. varius—and 3 or 4 undetermined species. Spondylus quinquecostatus is common. Casts of Conus, Venus, Cardium, Turritella, Haliotis, Murex, Fusus, and other genera are not uncommon.

The Echinodermata amount to 25 species, of which ten seem peculiar, whilst Clypeaster alius, G. marginatus, and Cidaris melitensis are among the most common species, and they are likewise met with in the Sand bed.

II. The is the most variable of all the formations, both as relates to its mineral composition and its organic remains. The point of transition between it and the Red Limestone is often im- perceptible, the latter gradually becoming less compact and more granular until it degenerates into an indurated red sand made up more or less of the Heterostegina depressa, which forms horizontal bands along cliff-sections or lies in disordered masses throughout many feet perpendicularly. These characters are displayed in cliff- exposures south of Dingli in Malta, and in the ravines of Emthaleb and Ramla Bay in Gozo.

Sometimes the Upper Limestone gradually merges into a black indurated sand composed of particles of glauconite, felspar, topaz, &c, which forms a variegated bed made up of black, green, brown, and red sands intermixed and stratified. This variety is well seen on the scarp of the hill of Chelmus in Gozo, where it is fully 30 feet in thickness. Altogether the greatest depth attained by the Sand bed may be little less than 60 feet.

The characteristic fossil of this bed is undoubtedly the Forami-