In the Fayûm, over a length of 80 to 90 kilometres, the basal beds of the Fluvio-marine series, at a height of only a few metres above the top of the Qasr el Sagha series, are frequently found to contain the remains of land-animals, often in sufficient quantities to form in places a true “bone-bed.” Besides land-mammals, remains of large tortoises, turtles and crocodiles, are very common, some of the latter being identical with those of the Qasr el Sagha series below. Chelonian and crocodilian remains are to be found on various horizons, but so far none but fragmentary mammal remains have been observed in the higher parts of the series. It is interesting to note that the bones in these beds appear to be most common near the accumulations of fossil trees, thus suggesting that they were floated out from the land at the same time and by the same river-currents. The porous character of the sands and sandstones of this group has resulted in the remains not being in nearly so hard or durable a condition, except when coated with ferruginous sand, as those in the series below, although the actual state of preservation is even more perfect. Analysis shows that these bones, with the exception of the loss of all organic matter, have undergone very little change. A sample examined by Mr. Lucas was taken from a typically preserved pelvis of _Arsinoitherium_ and gave the following result:— DETERMINED. CALCULATED. Silica 0·57 Silica 0·57 Oxide of Iron 1·98 Oxide of Iron 1·98 Lime 51·40 Calcium Phosphate 76·11 Magnesia trace Magnesium Phosphate trace Phosphoric Acid 34·86 Calcium Sulphate 4·64 Sulphuric Acid 2·74 Calcium Carbonate 14·75 Loss on ignition, Organic Matter nil being Carbon dioxide 6·13 Chlorine trace Sodium Chloride trace Not determined 2·32 Not determined 1·95 ------ ------ 100·00 100·00 The following composition of the bones of an ox, from an analysis by Berzelius, is appended for comparison:— % Phosphate and Fluoride of Calcium 57·35 Carbonate of Calcium 3·85 Phosphate of Magnesium 2·05 Soda and a little Sodium Chloride 3·45 Organic Matter 33·30 ------ 100·00 ------ It is curious that these Eocene bones should have so completely preserved their original composition considering the almost universal silicification of the trees deposited in the same beds.