=Gypsum and Gypseous Limestones.= The occurrences of gypsum and gypseous limestone beds in South-Eastern Egypt are restricted to the coastal regions. The most prominent of the deposits are those on Ras Benas (_see_ map on Plate XXI), where the beds form white hills rising to 188 metres above sea-level. Further north, gypseous deposits have been found by Dr. Hume to exist near the sea at Bir el Ranga, and by Mr. Ferrar the same beds have been recorded as occurring near the coast in the neighbourhood of Wadi Igli. It appears probable that the gypseous strata form a continuous or nearly continuous strip extending along the coast down to latitude 24° 22′, as shown on the geological map on Plate XX, but more complete observations may show that the distribution of the beds is somewhat different from that indicated. On the coast-plain south of Ras Benas, gypseous beds are not exposed except in the extreme south-east corner of Egypt, where they form small patches at Halaib and round the wells of Ti Kureitra. At Ras Benas, where the beds have been studied in most detail, they consist of gypsum and anhydrite [11,513][123] alternating with sandy marls and marly sands, forming hills much cut-up by steep sided narrow ravines. The weathered faces of the rocks are very soft, and the disintegrated material forms a stretch of soft gypseous sand, into which one’s feet sink four or five centimetres at every step, between the hills and the shore. At Halaib, gypseous limestones crop out from under the gravel of the coast-plain and form low banks; the gypsum is here associated with calcareous grits [12,152, 12,114] and conglomerates, the latter having boulders of igneous rock set in a calcareous matrix. Near Ti Kureitra wells, the gypsum exposures contain much crystalline selenite, blocks of this material being used in the masonry lining of the wells. Both at Bir el Ranga and on Ras Benas the gypsum is found to contain small pockets of native sulphur. No fossils have been found in the gypseous strata, and their geological age is uncertain. The beds are younger than the Nubian sandstone, since they overlie that formation at Bir el Ranga. Their occurrence only near the coast leads one to regard them as having been formed after the Red Sea occupied its present position; but whether they originated as direct gypseous deposits, or were produced by the alteration of pre-existent Cretaceous or Tertiary limestones is not yet quite certain. It is noteworthy that at Ras Benas, where the gypseous strata rest on diorite and hornblende granite, the igneous rocks are considerably altered as if by weathering, with a strong brick-red colour due to the oxidation of ferruginous matter. PLATE XXI. [Illustration: GEOLOGICAL MAP OF RAS BENAS Ball. Geography & Geology of South-Eastern Egypt. Photo-Metal-Process. Survey Dept. Cairo 1910. (60-190)] =The Nubian Sandstone.=