13(3 DB.W. P. HUME ON SECULAE OSCILLATION IN EGYPT [Feb. I 9: 



The Middle Eocene. 



One of the best-known sections of this formation is displayed in 

 the Moqattam Hill above Cairo, and has been carefully studied by 

 Fraas, Schweinfurth, Mayer-Eymar, Blanckenhorn, Fourtau, and 

 Barron. The strata displayed in the cliff behind the citadel differ 

 widely, the lower two-thirds consisting of snow-white limestones, 

 while the upper red-brown series is characterized by the presence 

 of numerous beds of detrital materials, mainly sands and clays, 

 the organic contents of which also indicate their shallow-water 

 origin. This marked topographical and lithological separation led 

 Zittel to subdivide the Middle Eocene strata into the Upper and 

 Lower Moqattam divisions, these being undoubtedly due to im- 

 portant geological changes. 



It is now known, from further study, that to obtain an absolute 

 definition for these divisions is very difficult, seeing that they have 

 many points in common, and any means of distinction adopted in 

 one locality fails when applied to the whole of the Middle Eocene 

 deposits developed in Egypt. In the Fayum, for instance, the 

 detailed stratigraphical labours of Mr. Beadnell 1 have made this 

 region classical ground, and comparison of the results with those 

 near Cairo show broad differences alike in thickness, fossil contents, 

 and lithological character. 



The Lower Moqattam Series. 



This series has a great extension in Northern Egypt, the abund- 

 ance and variety of its fossil contents with the especial dominance 

 of large nummulites, Echinolampas, ScMzaster, and the crab Lobo- 

 carcinus, bearing testimony to the continued prevalence of marine 

 conditions throughout Northern Egypt. My recent examination 

 (1909) of the Western Desert between the Nile, the Fayum, and 

 Baharia Oasis has revealed a very definite system of zones, which 

 it is well to record for comparison with the Lower Moqattam 

 succession determined elsewhere. 



The observations between the Nile Valley at Beni Suef and the 

 Moela Oasis have brought into prominence a bed of more than 

 local interest, which forms both the summit of the series and of an 

 extremely level plateau in the region round the Moela and Rayan 

 Oases. The upper portion of this bed near Moela contains a very 

 globular variety of Lucina pJiaraonum Bell, accompanied by 

 crustacean remains ; the lower half, on the other hand, consists 

 almost entirely of minute Porocidaris spines, the bryozoan Eschara 

 duvali Mich., and other sea-urchin spines which M. Fourtau has 

 recognized as belonging to ffliabdocidaris gaillardoti Gauth. The 

 most characteristic feature, however, is the frequent presence of 



1 See Geol. Surv. Egypt Mem. on the Fayum (1905), with the discussions 

 of the interesting vertebrate fauna by Dr. 0. W. Andrews, and of the inver- 

 tebrate palaeontology of the district by Dr. M. Blanckenhorn. 



