In the Middle and Upper Eocene beds we first obtain an idea of the animals which inhabited Africa in Tertiary times, and the collecting and working out of this fauna will throw much light, not only on our actual knowledge of the African vertebrata of the Eocene period, which was practically nil until the discovery of the remains here described, but also on other wider biological questions, such as the origin of certain groups of animals, some of which were evolved in this part of the world. As recently pointed out by a writer in the Field (No. 2605, Nov. 29, 1902) many years ago the late Prof. Huxley, to account for the present distribution of the mammalian fauna of Africa and Magadascar, advanced the theory that in the early part of the Tertiary period Madagascar was connected with Africa, and Africa with Europe or Asia, a connection which allowed of the immigration into Africa and Madagascar of numerous small types of European and Asian mammals. Madagascar later becoming separated from the mainland, its fauna, undisturbed by the larger carnivora, was able to develop to its present remarkable extent. Subsequently to the isolation of Madagascar the ancestors of the modern fauna were presumed to have invaded the African continent from the north. The extinct fauna of the Fayûm, however, shows that in early Tertiary times Africa already had its own mammalian fauna, which, besides containing some remarkable large types of somewhat doubtful position, such as _Arsinoitherium_, _Barytherium_, etc., certainly in _Mœritherium_ and _Palæomastodon_ included the earliest known elephants, the forbears of the Mastodon and the modern elephants. There is little doubt therefore that in Upper Eocene and Oligocene times these early members of the elephant group ranged northward and eastwards into Asia and India, and since in the Upper Tertiary deposits of India and eastern Asia the extinct transitional types between the mastodons and modern elephants appear to have been found, it is not unlikely that during the later phases of the evolution of this group of animals the radiation was back towards Africa, so that the African elephant may be, as it has usually been regarded, an immigrant from the Oriental region. Further research among the later deposits of the Fayûm and the deserts to the north may, however, throw an entirely new light on the subject and it is somewhat premature to theorise at present. [Illustration: PLATE XII. RAISED BEACH UNCONFORMABLY OVERLYING MIDDLE EOCENE LIMESTONES (BIRKET EL QURUN SERIES) IN THE DESERT EAST OF SIRSENA.]