Shortly after my arrival in Cairo, Dr. Schweinfurth, of that city, was so kind as to conduct me to a remarkable sea-terrace at the foot of the Mokattam hill, behind the tombs of the Caliphs, and stated, on the authority of Col. Ardagb, R.E., to be at an elevation of about 200 feet above the level of the sea, and which, I believe, was first described by Oscar Fraas. At this place a cliff of hard Eocene limestone, about 30 feet in height, has been perforated by Lithodomi, whose burrows are now filled with a grey calcareous deposit, and valves of a small species of oyster are also attached to the surface of the rock. The burrows resemble those of an ordinary Mediterranean species of Lithodomus, but I did not see the shells. The oyster has been described by Fuchs as a new species, under the name O. pseudo-cucullata; but, according to Dr. Schweinfurth, it does not seem distinguishable, except as a variety, from O. cucullata, Born. (=O. Forskali, Chemn.), of the Red Sea. Since the locality was observed by Fraas, Dr. Schweinfurth has discovered other shells in the crevices of the rock, more especially a Pecten, a Terebratula, and a Balanus, all modern species. The recent character of these shells and their mode of occurrence and state of preservation, oblige us, I think, to assign them to the Pleistocene, or at farthest the later Pliocene period, though I am aware that they have been regarded as Miocene.