138 DK. W. F. HUME ON" SECULAK OSCILLATION" IN EGYPT [Feb. igil, 



In descending the eastern scarp bounding the depression of Wadi 

 Muela, the succession is seen to be as follows : — 



1. Siliceous, cavernous limestone, with the globulose Lucina pharaonum 



Bell, and crustaceans. This is Mayer-Eymar's I. d, in which he 

 also records Gisortia, JRostellaria, and Eschara duvali Mich. 



2. White chalky limestone, made up of Porocidaris spines, and containing 



flints. (Apparently not recognized by previous writers.) 



3. Greyish-yellow marls with Gn/phcsa pharaonum Oppeuh.: rich, not only 



in that species, but also in Spondylus <egyptiacus R. B. Newton, 

 Velates schmiedeli Chem., and the large species of Echinolampas. 



4. Marls with Pecten moelehensis M.-E. and Vulsella chamiformis M.-E. 



Small nummulites are present throughout the series. 



5. Clays with gypsum, probably 6 metres thick, and, so far as personal 



observation goes, without fossils, overlying 



6. The Nummulites-gizehensis Beds, forming the floor of the valley. These 



west of Moela contain very large Nautili and Exogyra fraasi M.-E. 



Some 40 kilometres to the westward the beds No. 3 were of 

 especial interest, owing to the great abundance of the smaller sea- 

 urchins, which include Echinolampas crameri de Lor., Thylechinus 

 libycus Fourt., Mistechinus mayeri de Lor., etc. 1 In addition, 

 Exogyra fraasi M.-E. is very abundant, also the small nummulites, 

 and a few specimens of Carolia, Solarium, Plicatula polymorpha 

 (rare). It will be seen that in these Lower Moqattam Beds the 

 Upper Moqattam fauna is already clearly indicated, so that the 

 upper line of demarcation is not sharply marked. 



As regards the lower line of demarcation, Dr. Blanckenhorn, in his 

 * Neues zur Geologie & Palaontologie JEgyptens ' (p. 422), states 

 that, on the eastern side of the Nile, there is a transition from the 

 underlying Upper Libyan Beds of the Lower Eocene to the Lower 

 Moqattam Series. The former is to a large extent characterized 

 by the presence of Alveolina ; but he found in Wadi Telat 

 Yusef, 24 kilometres east-south-east of Fashn, Alveolina cf. ob- 

 longa d'Orb., associated with Nummulites gizehensis, N. lamarcki, 

 and his species N t porosa. In general, however, there is a sharp 

 distinction between the Middle and the Lower Eocene, the main 

 points being : — 



(i) The upper beds of the Lower Eocene are characterized by Alveolina, 

 while the lower beds of the Middle Eocene are characterized by the 

 large nummulites of which Nummulites gizehensis is the type. 



(ii) The Middle Eocene is distinguished by the larger forms of the sea- 

 urchin Echinolampas {E. fraasi, etc.), the species of this genus in the 

 Libyan Beds being smaller and less widely distributed. 



(iii) The Conoclypeus delanouei de Lor., on the other hand, characteristic 

 of the Libyan Beds, is rarely represented in the Middle Eocene. 



(iv) The Moqattam Series is especially marked by the large size of the 

 oysters (Ostrea fraasi, etc.) and the genus Carolia. In the Libyan 

 Beds oyster-layers are often abundant, but in general these are rela- 

 tively small (0. multicostata Desh., etc.). 



(v) In the Middle Eocene siliceous concretions are comparatively rare, flinty 

 concretions being only marked in the Gisortia Beds ; in the Lower 

 Eocene silicification has proceeded on a large scale, beds of flinty 

 concretions forming conspicuous features throughout the series. 



1 R. Fourtau, ' Description des Echini des fossiles, &c.' Mem. Inst. Egypt. 

 vol. vi, fasc. ii (December, 1909) p. 171. 



