The accompanying profile (Fig. 4), measured during a hurried visit to the island for the purpose of correlating these beds with those of the mainland, shows the character of the lower beds of the Birket el Qurûn series at this point.[53]

The upper beds of the Birket el Qurûn series in this part of the Fayûm are lithologically similar to those just described, consisting of alternating clays and sandstones, about 37 metres thick. They are, however, generally much richer in fossil remains, which are likewise usually better preserved than in the lower beds. Some of the brown sandstones of this series are literally crowded with perfect examples of many of the typical mollusca; and further west, near the end of the lake, foraminiferal bands again become noticeable. Near Dimê the escarpment of these and the lower beds is gentle and inconspicuous, but followed westwards it becomes a bold precipitous cliff, increasing in height towards the western end of the lake, where it is capped by the lower beds of the Qasr el Sagha series.

The following section was measured on the mainland[54] opposite the island Geziret el Qorn.

Top.			Metres.
	1.	Gypseous clays, separated by a band of brown sandstone crowded with white well-preserved shells, including numerous individuals of Plicatula polymorpha, Ostrea, Turritella and Lucina pharaonis. Large vertebrae of Zeuglodon Isis occur on this horizon further to the north-east	8
	2.	Sandstones and gypseous clays. Although here the sandstones are not hard or predominant, this bed is equivalent to the hard sandstone full of borings capping the plain between the ruins of Dimê and the top of the escarpment overlooking the lake. Further north this bed often contains numerous Carolia placunoides and Ostrea	3
	3.	Gypseous clays	3
	4.	Clays, brown sandstones, and occasional beds of limestone, often very fossiliferous, containing Ostrea Reili, Carolia placunoides, Cardita Viquesneli, d’Arch., Lucina sp., Turritella pharaonica,[55] Clavelithes longævus, Qerunia cornuta, etc., etc.	10
	5.	Clays with fossils as in last bed, capped by hard band of shelly sandstone	3
	6.	Alternating yellow-brown sandstones and gypseous clays	10
		Total thickness	37
	Bed with weathered-out sandstone concretions at top—upper bed of section at Geziret el Qorn.[56]

At the western end of the Birket el Qurûn the series is well marked, the sandstone beds forming the steep face of the bold precipitous cliffs which are so marked a feature at this end of the lake. The group has a thickness of some 50 metres and is overlain by the lower beds of the Qasr el Sagha series; it is more convenient here to give the entire section of the cliffs down to the base of the series under discussion:—

Top of Cliffs.				Metres.
1.	Hard grey sandstone and shelly limestone passing up into calcareous sandstone (forming surface of plain dipping north).		Lower part (42 metres) of Qasr el Sagha Series.
2.	Impure sandstone with numerous fossils:—Qerunia cornuta, corals, Ostrea Reili, O. Clot-Beyi, Carolia placunoides, Plicatula polymorpha, Cardita (? fajumensis) sp., Clavelithes longævus, Serpula, etc.
3,	4. Clays with band of argillaceous sandstone. Septaria bed near base. Fish-remains.
5.	Earthy limestone crowded with Ostrea Clot-Beyi, O. sp., Plicatula polymorpha, Pecten sp., Lucina sp., Cytherea sp., Turritella sp., Nonionina sp., Oliva sp., Pleurotoma sp., Vermetus sp., Nautilus sp.
6.	Thin-bedded clays, grey with yellowish band, sandy clays interbedded with soft whitish sandstones with small irregular concretions. Clays, gypseous and sometimes carbonaceous.
7.	Shelly sandstone, hard on upper surface and very fossiliferous (forms similar to Bed 9).
8.	Gypseous clays.
9.	Thin (·25 to ·5 metre) hard dark reddish-brown, very ferruginous, concretionary-weathering sandstone with nummulites and Operculina and well-preserved examples of Qerunia cornuta, Pecten sp., Pectunculus sp., Venus sp., Cardita Viquesneli, Astarte sp., Macrosolen Hollowaysi, Lucina sp., Natica sp., Cerithium sp., Clavelithes longævus, Voluta sp., Dentalium sp.			1
10.	Hard purplish clays			7
11.	Soft yellowish sandstone with Ostrea sp., Cardita ægyptiaca, Lucina sp., Turritella sp., and sharks’ teeth. Upper surface tends to become dark, ferruginous, and concretionary			1
12.	Purple clays, with strings of gypsum			6
13.	Soft light-yellow sandstones with harder shelly bands and occasional concretionary beds, forming vertical cliff-wall			17
14.	Grey and brown clays			18
Ravine Beds.		Total		50

In the cliffs west of the end of the lake the upper bed No. 9 continues highly fossiliferous and yields the most perfectly preserved molluscan remains to be found in the Fayûm and probably in Egypt.

A few kilometres east of the end of the lake a band of large globular concretions occurs in the thick brown sandstone forming the vertical face of the cliff. In many places the effect of weathering of these rocks is of some interest, numerous “earth-pillars” having been formed; these are largely the result of the action of blown sand, assisted by rain, the concretions being left capping pillars of brown sandstone, the sides of which are sculptured by the wearing action of sand. The curious perforate or cellular appearance which the weathered surfaces of this sandstone assume after long exposure are particularly noticeable in this neighbourhood and in the Zeuglodon Valley further west.

In the well-marked hill distant 17 kilometres to the north-east of Gar el Gehannem, the soft fossiliferous sandstones of this series are crowded with Operculina, Nummulites, and many species of mollusca beautifully preserved.

At Gar el Gehannem the series is seen (Fig. 2 and detailed section page 36) forming part of the slope of the hill, underlain by the Ravine beds, and capped by part of the Qasr el Sagha series. It here consists of yellow sandstones divided by a bed of clay; the sandstones are often crowded with nummulites (of two species); also Operculina (discoidea?), echinids, Balanus sp., Ostrea Reili, O. Fraasi, Carolia placunoides, and species of Pecten, Pinna, Cardita, Teredo, Turritella, and Cerithium.

In the Zeuglodon Valley, 12 kilometres W.S.W. of Gar el Gehannem, the brown sandstones of the Birket el Qurûn series are divided by a narrow band of fine-bedded grey clay. Most of the fantastically shaped hills on the south-west slope of the valley are carved out of the lower division of the sandstone. The concretionary beds of the Birket el-Qurûn series are not developed in this neighbourhood. Remains of Zeuglodon of both species (Z. Osiris and Z. Isis) are remarkably abundant and the skeletons of these cetaceans may be found in every stage of weathering. The larger species, Z. Isis, is the more common, and series of vertebrae, twelve to fifteen in number, can frequently be counted in situ. The remains are most abundant enclosed in the hard brown nodular bands of the series but in such cases it is almost impossible to extract specimens of any value. In one instance an almost complete skull of Z. Isis, measuring 116 cm. in length, was found enclosed in a large block of the nodular rock.[57] Bones are frequently to be observed protruding from the wind-worn sides of the small hills, while those portions of the skeleton already weathered out litter the ground below. Exposed they break up with rapidity, although where the enclosing rock is softer than the bone itself, parts of the skeleton beautifully preserved and perfectly free from matrix may sometimes be obtained.

The molluscan fauna is represented by very large numbers of pseudomorphs in sulphate of strontium (celestine) of the genera Lucina, Turritella, Fusus and Nautilus, the profusion of individuals of a species of the latter being very marked. In the case of lamellibranchs the radiating bundles of crystals of celestine are seen to originate from a point placed centrally on one of the valves, so that on this side (of a slightly weathered example) a radiating mass of crystals is seen, while on the other appear numerous contiguous circular areas, representing the terminal ends of the bundles of crystalline fibres or needles. Apart from the quantities of organic pseudomorphs, masses of crystalline celestine occur in the sandstones throughout the valley, and altogether the quantity of sulphate of strontium present must be very great. The gigantic oysters and other fossils which occur in some of the overlying higher beds, and the numerous individuals of nummulites in the sandstone itself, never seem to be replaced by celestine.

Nummulites of two species are very abundant in some bands and the presence in the Zeuglodon Valley of occasional individuals of the large N. gizehensis shows that in favourable localities this species persisted throughout the time represented by the deposition of the Ravine beds and ranged upward into the basal members of the Birket el Qurûn series.

In the higher hills within the valley, and in the hill-mass on the south side, the yellow sandstones of the Birket el Qurûn series pass up into the basal members of the Qasr el Sagha series. In their upper limits the sandstones become very nummulitic in places and at the top bands made up of Carolia and Ostrea occur. Above these, in the basal members of the Qasr el Sagha series, huge oysters and finely preserved specimens of Qerunia cornuta are conspicuous.

The dip in the valley is 2° north.

The southern face of the hill-mass lying immediately to the south of the Zeuglodon Valley is an almost sheer cliff of over 100 metres, descending to the silt covered basin below which has already been noticed (page 23). On this escarpment the hard nodular marly limestones of the Ravine beds are seen near the base, overlain by a mass of grey shaly gypseous beds; above, forming as a rule a vertical wall of rock, lies the hard massive brown sandstone of the Birket el Qurûn series, here undivided by clays; at the top, highly fossiliferous alternating clays and limestones are found forming the summit of the hills.

The exact junction between the Birket el Qurûn series and the overlying Qasr el Sagha beds is naturally perfectly arbitrary, many of the fossils being common to both groups. Carolia placunoides, which is perhaps the most abundant fossil in the Qasr el Sagha series, is sometimes very common in the upper beds of the underlying group, and, as shown before, is common enough in the still lower Nummulites gizehensis beds of Wadi Rayan. So that, though this fossil itself is no criterion, its relative abundance in the upper series justifies those beds being called the “Carolia beds,” the additional name of the Qasr el Sagha series being taken from the old ruin of that name where these beds are fully seen.

D.—Qasr el Sagha Series (Carolia Beds).

This division is strikingly developed in the north of the Fayûm, where it forms a bold escarpment of great length, consisting of an alternating series of very fossiliferous clays and limestones, with sands and sandstone in the upper beds, of a total thickness of 175 metres.

This series is the equivalent of the well known Upper Mokattam beds of Jebel Mokattam, immediately to the east of Cairo. The cliffs of this hill are among the best known in Egypt and have been studied by many geologists, including Zittel, Schweinfurth, Mayer-Eymar, etc.; these authors have classified the whole of the Upper Mokattam of Cairo as equivalent to the Upper Parisian (Middle Eocene) of Western Europe. The series is far better developed in the Fayûm than at Jebel Mokattam, where the total thickness is only some 70 to 80 metres.

In consequence of the discovery in these beds of a highly interesting vertebrate fauna, including land animals, the series becomes of the greatest importance. As already mentioned, as long ago as 1879, Schweinfurth, during a journey across the Fayûm, obtained remains of Zeuglodon in the underlying series from the island in the Birket el Qurûn. Subsequently[58] he obtained additional remains of the same cetacean in a violet marl belonging to the present series, from a locality 12½ kilometres west of Qasr el Sagha[59]; these remains, as already mentioned, were described by Dames as Z. Osiris. Since then important finds of land and marine mammals and reptiles have been made in different beds of this series; these will be referred to later.

The outcrop of the Qasr el Sagha series occupies a large part of the northern desert of the Fayûm. The beds are, however, best seen in the cliffs about 8 kilometres north of the Birket el Qurûn, where they form a steep double escarpment, running east and west, nearly parallel to the northern shore of the lake. The dip of the series being northward at a very low angle, and the upward slope of the ground being in the same direction, this cliff dies out a few kilometres north-east of Qasr el Sagha. A little further north, however, a N.W.-S.E. fold and fault again exposes nearly the whole of the beds of the series, forming prominent cliffs as before.

In the conspicuous hill 17½ kilometres 28° N. of E. (magnetic) of Tamia the series consists of innumerable alternations of clays and sandy limestone. The calcareous beds nearly always contain numerous examples of Carolia placunoides, Ostrea and Turritella of several species, but other well-preserved fossils are rare. The exposed beds here have a thickness of about 55 metres, and are underlain by the Birket el Qurûn beds with a well-marked band of concretionary sandstone, the thickness of the two series together being 127 metres. The upper beds of the former series are not here exposed, the top of the hill being formed of well-rounded flint and quartz pebbles embedded in a base of finely crystalline gypsum (2 metres thick), a deposit of Pleistocene times.

To the north of Tamia a large area of desert is occupied by the beds of this series; the district has the character of an undulating plain with occasional groups of hills and low irregular escarpments. At the groups of hills 12 kilometres N.N.E. of Tamia, and just to the east of Garat el Faras, the Qasr el Sagha beds are found to consist as usual of an alternating series of sands, sandstones, clays, marls and limestones, with numerous individuals of Ostrea, Carolia and Turritella, besides vertebræ, teeth and spines of large fish.

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.

Top.		Thickness 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
5.	Sandy, glauconitic clays with gypsum; oyster-bed at base in places. Alectryonia Clot-Beyi, Bellardi, Exogyra Fraasi, May.-Eym.	10
2nd escarpment.
6.	Hard or friable limestone, sometimes sandy, full of Carolia placunoides, Cantr., and Exogyra Fraasi, also Ostrea aff. heteroclyta, Defr., Ostrea Reili, Fraas., O. elegans, Desh., Plicatula Bellardi, May.-Eym., Pectunculus (?) ægyptiacus, Oppenh., Qerunia (Hydractinia) cornuta, May.-Eym.	2
7.	Purplish clays interbedded and remarkably current-bedded with ash-grey sands, with both ferruginous and highly carbonaceous bands with plant-remains, lignite and natural charcoal. Vertebrate remains fairly common, the mammalian including Zeuglodon Osiris, Eosiren libyca, Andr., Mœritherium Lyonsi, Barytherium? Andr.; the reptilian Stereogenys Cromeri, Andr., and Tomistoma africanum, Andr., with numerous coprolites; also frequent remains of siluroid and other fish. Masses of coral, Astrohelia similis, Felix, in places	12
8.	Hard grey, close-grained, concretionary sandstone, frequently weathering into huge elongated rounded masses; Turritella pharaonica, Cossm.
	Hard, purplish clays with grey sandy clays, sandrock, etc. Occasional crocodile and fish-remains	4
9.	Hard ripple-marked sandstone. False-bedded sandstones with clay partings; ferruginous and lignitic bands with lumps of lignite. Occasionally coprolites and remains of Sirenia and Crocodilia are numerous	7
10.	Hard or friable brown sandy limestone with shell-casts filled with scalenohedra of calcite. Carolia placunoides, Turritella sp.	½
11.	Gypseous clays, with red ferruginous band; weathering to paper-shales below	4½
12.	Light-yellow limestone and calcareous sandstone with sharks’ teeth, Mesalia fasciata, Lam., Cassidaria sp., Rimella rimosa, Sol., Trachelochetus bituberculatus, Cossm., Turritella carinifera, Desh., T. Lessepsi, May.-Eym., Cardita fajumensis, Oppenh. Goniopora?	1
13.	Slate-blue and brown gypseous clays with band containing Mesalia sp., Cassidaria nilotica, Bell., Exogyra Fraasi and Goniaræa elegans	3
14.	Sandstone and sandrock, light yellow	1
15.	Yellow sandy friable limestone with casts of shells and Mesalia fasciata, M. oxycrepis, May.-Eym., Turritella Lessepsi, T. pharaonica, Cossm., Alectryonia Clot-Beyi, Ostrea Reili	½
16-17.	Sands, sandy clays and clays with a double band of limestone containing Ampullina hybrida, Lam., Melongena nilotica, var. bicarinata, May.-Eym., Tudicla aff. umbilicaris, May.-Eym., Turritella Lessepsi, T. parisiana, May.-Eym., Solarium sp., Alectryonia Clot-Beyi, Plicatula polymorpha (occasional), Lucina fortisiana, Defr., L. pharaonis, Bell., Mytilus affinis? J. and C. Sowerby, Astrohelia similis, Goniaræa elegans, Mich.; numerous vertebrate remains both above and between limestones including Zeuglodon Osiris, Eosiren libyca, Barytherium grave, Andr., Moeritherium Lyonsi, M. gracile, Andr., Gigantophis Garstini, Andr., Pterosphenus Schweinfurthi and Tomistoma africanum, Andr. The remains of a siluroid fish are abundant; also Propristis Schweinfurthi, Dames. Large numbers of coprolites. Silicified wood	12
18.	Brown sandy limestone with casts of shells, Akera aff. striatella, Lam., Ampullaria, n. sp., Gisortia gigantea, Munst., Lanistes antiquus, Blanck., Melongena nilotica, var. bicarinata, Mesalia sp., Cassidaria nilotica, C. aff. nodosa, Solarium aff. bistriatum, Desh., Alectryonia Clot-Beyi, Cardium Schweinfurthi, Exogyra Fraasi, Lucina pharaonis, Bell., Macrosolen Hollowaysi, J. Sowerby, Meretrix nitidula, Lam., M. parisiensis, Desh., Ostrea flabellula, Lam., Tellina sp., overlying clays with gypsum	4
19.	Sandy limestone with numerous Carolia placunoides and Turritella imbricataria, Lam.	1
20.	Greyish-blue and brown ferruginous, sandy, and other clays. Plant remains	13
21.	Friable shelly limestone with occasional small calcite veins	½
22.	Clays	4
23.	Hard yellow sandy limestone with Ostrea and Anisaster (Agassizia) gibberulus	½
24.	Clays with thin bands of fibrous gypsum	6
25.	Hard friable shelly limestone with numerous fossils, including Dictyopleurus Haimi, Dunc. and Slad.; Akera aff. striatella, Turritella carinifera, T. imbricataria, T. pharaonica, Alectryonia Clot-Beyi, Arca tethyis, Oppenh., Cardita aff. carinata, J. Sowerby, C. aff. depressa, Locard., C. aff. triparticostata, Cossm., C. cf. gracilis and depressa, Locard., Cardita fajumensis, Cucullæa aff. crassatina, Lam., Exogyra Fraasi, Glycimeris (Pectunculus) pulvinatus, Lam., Ostrea aff. Reili, Spondylus ægyptiacus, Bull. Newt., Pecten solariolum, May.-Eym., P. moelehensis, May.-Eym., Qerunia cornuta, Euspatangus cairensis, Loriol, Linthia sp., Anisaster gibberulus, Schizaster aff. africanus, Loriol; bryozoa	½
26.	Sandy clays with gypsum	7
27.	Friable, gypseous, impure limestone with Exogyra Fraasi, Carolia placunoides, Turritella sp., Qerunia cornuta, Alectryonia Clot-Beyi	½
28.	Sandy gypseous clays	3
29.	Friable sandy limestone with Carolia placunoides, Exogyra Fraasi, Turritella sp. (The ruin of Qasr el Sagha is built on this bed)	1
30.	Gypseous sandy clays with occasional oyster-limestone with Qerunia cornuta; ferruginous sandstone band, etc.	27
	Total	154
Hard grey sandstone with Zeuglodon and numerous Carolia, Ostrea, etc., in places, capping plain to south of Qasr el Sagha and forming the top of the “Birket el Qurun series.”

The chief divisions of the series remain fairly constant and can be recognized and followed for many kilometres westwards.[61] The lower beds form the summits of Gar el Gehannem and the neighbouring hills (see Fig. 2 and section p. 36), the upper beds of the series being exposed in the higher escarpments to the north.

Although vertebrate remains are more common on some horizons[62] than on others, they are occasionally met with in most of the beds. The most prolific bone horizon is, however, about half-way down, i.e., those beds numbered 16 and 17 in the above section; bed 7 also yielded a number of remains. At the point where the upper part of the section was measured, 3½ kilometres north-east of Qasr el Sagha, the beds 16 and 17 yielded a considerable number of land-animal remains, all of which occurred within a fairly confined space, suggesting that they had been carried out from the land to this point by a strong river-current and deposited when the latter became too feeble to carry them further out to sea. The same beds were also examined in the faulted bay 8 kilometres to the north, but no bones, or at most a very occasional fragment or two, were obtained here. This is easily explained by the greater distance of this locality from the land-mass to the south. Westwards the same beds were always found more or less bone-bearing, isolated detached mandibles, limb-bones and vertebræ of Mœritherium, being of frequent occurrence, although no such complete remains were found as those from near Qasr el Sagha. Reptilian and fish bones are very widespread throughout the area. An extensive and detailed examination of these beds over a large area can hardly fail to yield important results, as other localities where skeleton-carrying currents came out from the land would very likely be discovered.

That the Qasr el Sagha series was deposited in fairly shallow water at no great distance from land seems certain, not only from the general lithological character of the beds but from the number of land-animal remains and the frequency of river and shore-frequenting whales, dugongs, crocodiles and turtles. The clays, moreover, are found to abound with impressions of plants, and in some cases are highly lignitic, being made up of compressed masses of vegetation including solid twigs, now found in a state more resembling charcoal than ordinary dense lignites; some bands approximate to an impure brown coal. In certain beds of the series further to the west, very thin seams of true coal occur; they were, however, never seen to exceed one or two millimetres. The intercalated bands of limestone are generally impure and do not indicate any great conditions of depth, but only rather a temporary cessation in the supply of sand and clay. Corals, moreover, abound along many horizons.

Section XI.—UPPER EOCENE (BARTONIAN)—LOWER OLIGOCENE.

E.—Fluvio-Marine Series (Jebel el Qatrani Beds).

Throughout the north of the Fayûm depression the Qasr el Sagha beds, forming the uppermost Middle Eocene, are followed by an unique series[63] of variegated[64] sands and sandstones, with alternating beds of clay and clayey marl. The ever-recurring bands of limestone, so common to the underlying marine beds, have now almost completely disappeared, being represented by only an occasional bed of calcareous grit, marl, or thin band of limestone. In the upper part of the series occurs a horizontal sheet of basalt,[65] in all probability contemporaneously interbedded; this forms a convenient datum line and may perhaps be provisionally taken as an arbitrary junction between the Eocene and Oligocene. Although as a rule remarkably barren of organic remains, certain bands, especially in the upper part, yield numerous individuals of a few species of mollusca, including Lucina, Arca, Mutela, Spatha, Unio, Lanistes, Turritella, Melania, Potamides, Cerithium and Pleurotoma. From such an assemblage we may without doubt conclude that the conditions under which the series was deposited were estuarine or fluvio-marine, and this is further proved by the non-marine lithological character of the beds. The enormous quantities of silicified wood which occur in certain beds, in the shape of hundreds of trees of great length and girth, together with the numerous remains of land-animals, crocodiles, tortoises and turtles, indicate that rivers of considerable size emerged from the land to the south, the coast-line of which was probably not far distant. In fact the retreat of the sea, which as already mentioned, had probably already begun in Middle Eocene times, was now still further continued, although the cause of this was apparently not so much due to elevation of the land as to the continued deposition of sediment from south to north beyond the land-shore. We may in fact regard the series as a huge delta deposit in an area of local depression, in which the great accumulation of sediment brought down from the land continually caused the gradual retreat of the sea to the north.

The same conditions would even appear to have continued on to Pliocene times, as from the Fayûm northwards stretches an immense plain of lithologically similar rocks, evidently accumulated under similar conditions, and which appear to contain newer and newer faunas from south to north. Thus, while in the Fayûm the remains are of Middle and Upper Eocene and Lower Oligocene age, when the latitude of Mogara is reached, some 70 kilometres further north, a fauna distinctly Lower Miocene in aspect occurs; further north again, as at Wadi Natrûn, Pliocene remains are abundant. We may hope therefore that this otherwise barren desert, when carefully and systematically explored, will yield us a continuous record of the vertebrate life of the northern part of the African continent from Eocene to Pleistocene times.

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, being Carbon dioxide	6·13	Organic Matter	nil
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.

Most frequently the vertebrate remains are found in an unconsolidated false-bedded clean quartz sand, the grains of which are semi-rounded or angular; in some layers the sand is very coarse and polished, and mixed with fine gravel. These deposits of sand, apparently brought down by river floods, are not continuous along any particular horizon, but are intercalated here and there in the ordinary sandstones, clays and marls of the series; they occur chiefly, however, as local lenticular masses along a more or less constant horizon near the base of the series. The bone-remains are not absolutely confined to these deposits of river-sand, but like the silicified trees are far more common in them than elsewhere. Scattered mammal bones occur in the lower clays, marls, and hard concretionary sandstones, while the remains of aquatic animals, such as turtles and crocodiles, may be found almost anywhere.

From an examination of the series in the field, there is no doubt that, in at least the centre of the area, the deposition of the lowest beds was continuous with those of the Qasr el Sagha (Middle Eocene) series below. Followed away from the centre (i.e. the district round Widan el Faras, the eastern extremity of Jebel el Qatrani) the series gradually thins out, and eastwards, at Elwat Hialla, some 23 kilometres north of Tamia, has a thickness of only 40 metres, the basal beds being apparently laid on to a bed of limestone of the Qasr el Sagha series about the horizon of Bed 12 in Section XXIII. The junction here is apparently one of perfect conformity as far as the individual beds go, and the peculiar sequence does not seem to be due to ordinary overlap; it appears as if the change from marine to estuarine conditions had set in earlier here than further to the west, with the result that the upper Qasr el Sagha beds are wanting. Moreover, the accumulation of estuarine beds went on so slowly in this locality that the series does not attain to nearly its normal thickness, while further east it dies out altogether. The slight dip to the north is identical in both series, their lithological characters being, however, very different.

Although the Qasr el Sagha series contains numerous bands of clay and sandstone, the continual recurrence of thick beds of limestone at once gives it a distinguishing feature from the group under discussion; the latter is in fact characterized by the highly-coloured sandy, and to less extent clayey, character of its beds. While the Middle Eocene is essentially marine, the succeeding formation marks the retreat of the sea and the incoming of estuarine and brackish water conditions.

Before discussing the age of the Fluvio-marine series it will be well to describe its development in the field. The beds of the complex are throughout the district always found following on above the Qasr el Sagha beds, although their thickness varies considerably, as might be expected in a series of this nature. The most easterly locality to which the formation was mapped is the scarp 23 kilometres due north of Tamia, known as Elwat Hialla. Here the beds form a separate escarpment, consisting of only about 40 metres of sands and sandstone grit (sometimes silicified) with pieces of silicified wood: some of the beds of sandstone have a concretionary stem-like weathering. From this point these beds extend westwards far beyond the western end of the lake, always forming the highest escarpments of the Fayûm depression. A kilometre or two from our most easterly point the first basalt sheets are seen, and these, preserving the same level as far as can be observed, continue some 60 kilometres further west, to a point nearly due north of the western end of the Birket el Qurûn. The series, only 40 metres thick at the eastern end, gradually thickens as it is followed westward, until it reaches its maximum development in the cliffs of Jebel el Qatrani, north-west of the temple of Qasr el Sagha, where a thickness of some 210 metres is attained.

Just 29 kilometres N.N.E. of Tamia (6 kilometres N.W. of the prominent western scarp of Elwat Hialla), a long hill offers a good section of these beds, which consist of a variegated group of green sands, red clays, coarse sandstones, red and yellow sand and sandstone, etc., capped by a band of hard impure yellowish limestone with numerous enclosed sand-grains (calcareous grit). Near the same place is an interbedded sheet of basalt, which is sometimes followed by another band of impure limestone and the latter by false-bedded sandstone. Huge logs of weathered-out silicified trees are seen strewn about.

The following is a detailed section of the series, measured from a point 3½ kilometres W.N.W. of Elwat Hialla, and about 28 kilometres N.N.W. of Tamia, to the top of the escarpment 4 kilometres further north:—

Undulating sandy, gravel-covered desert[66] stretching northwards.
Top of escarpment.			Metres.
1.	False-bedded sandstones		8
2.	Band of impure limestone
3.	Interbedded basalt sheet
4.	Sandstone
(Section continued in hill ¾ kilometre further north-east).
5.	Hard yellow limestone with enclosed sand-grains; cavities full of calcite		1
6.	Greenish-white sand-rock		1
7.	Hard reddish-brown stem-weathering sandstone		1½
8.	Greenish or white sand and sand-rock		3
9.	Variegated sandy clays; sand-rock with occasional fragments of bone		6
10.	White sand-rock		1
11.	Rose-coloured sandstone		2
12.	Hard grey white marly clays		2½
13.	Coarse yellow sandstone		5
14.	Reddish, white, and variegated sands and sand-rock		8
15.	Grey, reddish and yellowish clays, with bands full of plant-remains		3½
16.	Brown clayey, sandstone		2
17.	Greenish sandstone		1
18.	Sandy grey clay		1½
19.	Hard grey sandstone		½
20.	Greenish sand-rock and clayey sandstone		3
21.	Dark red clay		1
22.	Sands, etc.; outcrop of bed covered with silicified trees of large dimensions, 12-15 metres long		10
23.	Clays with hard grey false-bedded sandstone and showing fine mammilary weathering at top. Silicified logs on surface		8
24.	Red clays, sandy clays and argillaceous sands		4
25.	Reddish sand-rock		1
26.	Yellowish sand-rock, in part false-bedded		2
27.	Red clays with thin sandy bands		1½
28.	Coarse grey sandstone		2
29.	Red and green sandy clays with thin band of hard white sandstone at top		1
30.	Bright red clay		4
31.	Red clays with thin green sandy bands		3
32.	Greenish sand-rock with thin red clayey bands		1
33.	Reddish white mottled clayey sandstones passing up into red and white mottled clays and sandy clays		8
34.	Fine white sand		3
35.	Black ferruginous silicified sandstone
	Total thickness		90
Base.
Junction with Middle Eocene (Qasr el Sagha series).