134 DK. W. F. HUME ON SECULA.E OSCILLATION IN EGYPT [Feb. I 



yll. 



which the best sections are displayed, and partly to the vast 

 areas which still remain unexplored. 



r Nevertheless, there are indications of three well-defined divisions 

 in the Western Desert, as determined by my own studies, namely : — 



(1) Callianassa or Sismondia-logotheti Zone, or Upper Libyan. 



(2) Ostrea-midticostata Zone. 1 These c( 



(3) Opercidina-libyca Zone. J Zittel. 



(2) Ostrea-multicostata Zone. 1 These constitute the ' Lower Libyan ' of 



Zittel divided his series into two divisions, the Upper and the 

 Lower Libyan, using the Alveolines for the purpose. The spindle- 

 shaped Alveolina oblonga (?) Schwag. and A. frumentiformis Schwag. 

 mark the higher, and the spherical Alveolines the lower division. 



The Libyan Series. 



With regard to previous work on this subject, it may be noted 

 that Dr. Blanckenhorn, in his ' Neues zur Geologie & Palaontologie 

 JEgyptens,' recognized three divisions in the Lower Eocene, namely : 

 Lower, Middle, and Upper Suessonian, but some difference of 

 opinion has arisen with regard to the lower member, to which he 

 has also given the name of the ' Kurkurstufe.' The type-example 

 of these beds has unfortunately not been studied by anyone pro- 

 ficient in Egyptian palaeontology, since Sir William Willcocks first 

 drew attention to their existence at Gebel Garra, situated north 

 of the Kurkur Oasis, near Aswan. The strata occur in the form 

 of yellow clays 5 metres thick, overlying the Cretaceous paper- 

 shales and overlain by 90 metres of Lower Eocene limestone. The 

 fauna is of considerable interest, as described by Mayer-Eymar, in- 

 cluding Bothriolampas abundans Gauth. and Linthia lorioli M.-E. 

 The presence of the well-known Middle Eocene sea-urchin Poro- 

 cidaris schmiedeli Goldf. has also been recorded from here; but, 

 having had an opportunity of re-examining the original specimen 

 (now in the Cairo Geological Museum) with M. Eourtau, I feel 

 little doubt that it is the spine of a Rhabdocidaris. As Operculina 

 libyca occurs in the same matrix, the ' Kurkurstufe ' of Blancken- 

 horn in all probability represents the Operculina-libyca Zone, which 

 seems to be the lowest member of the fossiliferous Eocene over the 

 greater portion of Southern Egypt. 



If the Operculina-libyca Beds and the overlying strata with 

 Ostrea multicostata appear to be divisions of major significance, 

 much importance must also be attached to the Upper Libyan 

 division, owing to its widespread extent and special palseonto- 

 logical character. Zittel, as already remarked, separated these beds 

 from those below them by the nature of the Alveolines, and Mayer- 

 Eymar suggested that the base of the Upper Libyan should be 

 drawn at his Nummulites-biarritzensis layer, which according to him 

 seemed to occupy a constant geological position. At the typical 

 section in the Hill of the Tombs, or Gebel Dranka, west of Assiut, 

 this bed is above the tombs of the Kings, and at the base of a 



