24. Coarse unconsolidated false-bedded sands, with occasional bands of clay and consolidated sandstone bands. Numerous silicified trees and abundant mammalian and reptilian remains. (See list in Bed 49 of Widan el Faras section). Bone-pits are in this bed 40 25. Thin band (½ m.) of hard sandstone with sometimes } impure calcareous grit } } 10 26. Hard light yellow sandstone, often very coarse, } and with red bands } 27. Soft brick red and light yellow sands and sandstones, (seen on plain and overlying uppermost limestone of the Middle Eocene) 20 _Base of Fluvio-marine Series._ [Illustration: PLATE XI. SILICIFIED TREES OF FLUVIO-MARINE SERIES, 4½ KILOMETRES NORTH OF QASR EL SAGHA.] In some localities pebbly bands occur in the sandstone-grits, especially in some of the beds above the basalt: the pebbles are mostly quartz or flint, subangular or rounded, the layer averaging perhaps two cm. in diameter, although occasional specimens three or four times that size are met with. Silicified trees of two distinct types[75] occur, and they are met with chiefly on two horizons; usually large numbers of trees occur together, completely covering the surface in places; they lie as a rule scattered about in every direction, although occasionally a large proportion may show considerable parallelism of deposition, as if arranged by the direction of the current which floated them to the spot. They always occur in a horizontal position or parallel to the dip of the bed, and it seems quite certain that none of them ever grew near where they are now found. The trees never bear attached branches, the latter having always been broken off at or near the point of junction with the trunk, where the scars are often plainly seen; this points to the trees having been drifted a considerable distance. Many trees over 25 metres[76] in length have been met with, but this by no means represents the original height, as the trunks have lost considerably in length during transport to their present localities. Although, as a rule, found completely weathered-out and exposed on the surface, in numerous localities these silicified trees are to be observed firmly embedded in the sandstones in which they were deposited, many being met with in our excavations for bones. As the Fluvio-marine series is followed westwards from the central part of the area, the different divisions become more and more attenuated and the outcrops more and more obscured by superficial gravel. North-west of the Zeuglodon Valley an escarpment capped by a conspicuous bed of white calcareous grit occurs and perhaps represents the lower beds of the series. The higher are lost on the gravelly undulating plateau above.