Sandstone with hard ferruginous bands, full of _Exogyra_ 6·0 Sandy bed, crowded with well-preserved _Exogyra_ shells 0·2 Yellow sandy clay with numerous _Exogyra_ casts 3·0 Dark carbonaceous shale with obscure plant-remains } } 15·0 Sandy beds with bone-fragments } ----- _Floor of Oasis._ 168·0[41] At the extreme north end of the depression the cliffs and the lower part of the conspicuous dark hill, Jebel Horabi, are composed of shales, clays and sandstones belonging to this series. The cliffs are capped by Eocene limestone-grits and limestone as in the section just described. The upper part of Jebel Horabi, however, consists of a mass of ironstone, often coarsely pisolitic, with some limonite, and red and yellow ochre. This iron-ore appears to replace the sandy beds more or less irregularly at the base, but the great mass of mineral above is probably a later and quite distinct deposit. (_Vide_ under Post-Eocene). Traces of shells occur in places. In the isolated, limestone-capped hill (Plate I), 6½ kilometres north-west of Ain el Haiss (the northern spring) these beds are more fossiliferous than usual. _Top._ (Limestone, the basal bed of the intermediate series). Limestone, the basal bed of the intermediate series. Sandy beds with hard brown ferruginous concretionary } bands, containing numerous casts of _Cyprimeria_ } (_Artemis?_) _Arca_, _Cucullæa_, _Odostomopsis } abeitrensis_, _Baculites_ aff. _syriacus_, and } _Neolobites Vibrayeanus_ } } 50 m. Clays, often shaly } } Hard ferruginous sandstone with pockets of } clean white sand } Numerous other sections at different points were examined and measured. Such a series is naturally very variable, and individual beds do not maintain their characters over wide limits, so that correlation of different sections is not possible, except in the roughest manner. In the southern part of the depression fossils are more frequent, otherwise the beds are very similar. The series under consideration is by no means poor in organic remains, although the latter are more or less restricted to certain bands and localities. No doubt most of the fossil shells have been removed by solution, etc., as those now existing are generally preserved as pseudomorphs in limonite.