In consequence of the discovery in these beds of a highly interesting vertebrate fauna, including land animals, the series becomes of the greatest importance. As already mentioned, as long ago as 1879, Schweinfurth, during a journey across the Fayûm, obtained remains of _Zeuglodon_ in the underlying series from the island in the Birket el Qurûn. Subsequently[58] he obtained additional remains of the same cetacean in a violet marl belonging to the present series, from a locality 12½ kilometres west of Qasr el Sagha[59]; these remains, as already mentioned, were described by Dames as _Z. Osiris_. Since then important finds of land and marine mammals and reptiles have been made in different beds of this series; these will be referred to later. The outcrop of the Qasr el Sagha series occupies a large part of the northern desert of the Fayûm. The beds are, however, best seen in the cliffs about 8 kilometres north of the Birket el Qurûn, where they form a steep double escarpment, running east and west, nearly parallel to the northern shore of the lake. The dip of the series being northward at a very low angle, and the upward slope of the ground being in the same direction, this cliff dies out a few kilometres north-east of Qasr el Sagha. A little further north, however, a N.W.-S.E. fold and fault again exposes nearly the whole of the beds of the series, forming prominent cliffs as before. In the conspicuous hill 17½ kilometres 28° N. of E. (magnetic) of Tamia the series consists of innumerable alternations of clays and sandy limestone. The calcareous beds nearly always contain numerous examples of _Carolia placunoides_, _Ostrea_ and _Turritella_ of several species, but other well-preserved fossils are rare. The exposed beds here have a thickness of about 55 metres, and are underlain by the Birket el Qurûn beds with a well-marked band of concretionary sandstone, the thickness of the two series together being 127 metres. The upper beds of the former series are not here exposed, the top of the hill being formed of well-rounded flint and quartz pebbles embedded in a base of finely crystalline gypsum (2 metres thick), a deposit of Pleistocene times. To the north of Tamia a large area of desert is occupied by the beds of this series; the district has the character of an undulating plain with occasional groups of hills and low irregular escarpments. At the groups of hills 12 kilometres N.N.E. of Tamia, and just to the east of Garat el Faras, the Qasr el Sagha beds are found to consist as usual of an alternating series of sands, sandstones, clays, marls and limestones, with numerous individuals of _Ostrea_, _Carolia_ and _Turritella_, besides vertebræ, teeth and spines of large fish.