We may pass now to the locality where this series shows its best development and exposure, the beds being all concentrated in one bold escarpment, generally divisible into an upper and a lower cliff. These cliffs overlook the Birket el Qurûn, although distant usually about 8 kilometres, being separated from the lower escarpment of the Birket el Qurûn series (immediately above the lake shore) by a broad plain, the surface of which is usually the dip-slope of a hard bed of sandstone. From Qasr el Sagha (6½ kilometres N.N.E. of Dimê) these cliffs trend westward, keeping approximately the same distance from the north shore of the lake; they have been followed and mapped for a distance of 70 kilometres to a point 13 kilometres N.N.W. of Gar el Gehannem, whence they could be seen still trending in a direction slightly south of west (see Plate XVII). Small faults are of frequent occurrence along these escarpments, but are not of other than local interest; they almost invariably have their downthrow to the north, and it seldom exceeds a few metres. Fig. 5 shows a section through one of these faults near Qasr el Sagha. The following detailed section (Plate XXIII) will show the character of the beds forming this division. As might be expected in such a series, although the calcareous bands are fairly constant, there is a continuous change of character among the sandy and clayey sediments from point to point; the false-bedding is in places very striking. The main part of the section was measured 3½ kilometres north-east of Qasr el Sagha, but the lower beds not being exposed at that point, they were added from the cliffs at the ruin itself. The total thickness is 154 metres. Thickness _Top._ in metres. 1. Hard, white, grey-weathering, sandy limestone with numerous shell-casts: _Echinolampas Crameri_, Loriol, _Plicatula Bellardi_, May.-Eym. 2 2. False-bedded sand and sand-rock with grey and green clays; concretions and bands of ironstone. Hard, dark-brown or purplish ferruginous sandstone band. Occasional vertebrae of _Zeuglodon Osiris_, Dames, _Pterosphenus_ (_Mœriophis_) _Schweinfurthi_, Andr., crocodilian and fish- remains; coprolites 16 3. Hard, calcareous, ferruginous, clayey sandstone with brown ironstone concretions. Occasional fish- spines. Clays with massive veins of gypsum forming a stock-work, and left weathered out above surface. _Cardium Schweinfurthi_, May.-Eym., _Cardita fajumensis_, Oppenh., (_Cossmannella ægyptiaca_, May.-Eym[60]), _Crassatellithes_ sp. 9 4. Hard, yellow, gypseous sandy limestone or calcareous sandstone 1½