The same beds are exposed immediately to the east of the village of Sersena, midway between Sêla and Tamia. They are again well seen in the ravine below the last named village, and forming the narrow strip of the desert projecting into the cultivation as far as the northern end of the Tamia lake; they also occur on the shore of the latter at El Tuba, about 2 kilometres south of the village. At Tamia their exposure measures 25 metres in thickness. At various points along the north side of the Birket el Qurûn exposures of this series occur, the beds forming the lower sloping part of the cliffs overlooking the lake, as well as the base of the island “Geziret el Qorn,” although only the upper beds are visible above the water of the lake. Both here and along the northern shore of the lake they are for the most part hidden by the high level recent lacustrine clays, but where occasionally exposed their identity is certain, the characteristic small brown fish-scales being abundant, besides occasional teeth, with shell-impressions of the different genera enumerated above. [Illustration: PLATE VI. ESCARPMENT OF THE BIRKET EL QURUN SERIES NEAR THE WESTERN END OF THE LAKE.] At the western end of the lake the Ravine beds form the lower part of the cliff as well as the plain to the south; the underlying _Nummulites gizehensis_ limestone not being exposed. The series consists of some 45 metres of white and grey shaly marls with harder bands of siliceous limestone intercalated throughout, one of which usually forms the uppermost bed. It is, in fact, the development in places of one or other of these hard beds of limestone near the top of the series that gives rise to the bold promontories, or horns, which occur on the north side of the Birket el Qurûn. The greater part of the marls and clays met with from 18·5 to 112·5 metres below the surface in the boring at Medinet el Fayûm in all probability belong to the Ravine beds. The maximum thickness of this series is 70 metres, measured at Gar el Gehannem. _C._—=Birket el Qurun Series= (_Operculina-Nummulite Beds_). The above designation is convenient and applicable to these beds, which form the escarpment immediately overlooking the lake on the north side throughout its length.