Vol. 67.] THE GEOLOGY OF CYRENAICA. 599 



luciani ; hence this bed and the underlying Echinoid Limestone 

 may both be included in the Middle Eocene. The Fibularia Bed 

 is succeeded by a series of limestones which, so far as I saw, were 

 resting conformably upon it. These limestones include the white 

 to cream-coloured nummulitic limestone, in which have been 

 excavated the tombs of the northern necropolis of Cyrene. 

 Mr. Chapman refers the foraminifera in this rock to the Middle 

 Eocene. It does not, however, contain the typical N. gizehensis 

 found in the Derna Limestone, but the variety lyelli ; and that 

 variety is also found in the brown- weathering, stratified limestones 

 at Slonta. There and elsewhere the variety lyelli is associated 

 with Priabonian, or at least Upper Eocene, mollusca and echinoids. 

 I am therefore forced to the conclusion that the Slonta Lime- 

 stone should be included in the Upper Eocene, and regarded as 

 Priabonian. This view involves the correlation of the hard, 

 brown-weathering limestones of the Slonta Downs with the soft, 

 cream-coloured, nummulitic limestone of the northern necropolis 

 of Cyrene. But, as the two formations both occur between the 

 Cyrene Limestone and the Derna Limestone, and as they both 

 contain the same variety of nummulite, they must be approximately 

 on the same horizon. The difference in their lithological charac- 

 ters is probably due to the beds at Cyrene having been deposited 

 farther from land. The occurrence of the variety lyelli may be 

 due to its survival, owing to favourable bathymetric conditions. 



The identification of the Slonta Limestone as Upper Eocene 

 and Priabonian introduces one important difference between the 

 stratigraphical succession in Egypt and in Cyrenaica. The coral- 

 limestones of the two countries must be at different horizons ; but 

 what is more remarkable is that the great gap in the succession 

 in Cyrenaica would be later than that in Egypt, if the usually 

 accepted age of the Palceomastodon Beds of Egypt be correct. The 

 date of that fauna has been the subject of considerable dis- 

 cussion. According to Dr. Andrews, 1 these Palceomastodon Beds 

 are Bartonian ; Prof. Deperet, 2 on the other hand, from the resem- 

 blance of Andrews's Ancodon c/orrinc/ei from the Fayum to the 

 Bracliyodus cluai from the Ebro Valley, holds that the Fayum 

 Beds are Oligocene, and belong either to the base of the Stampian 

 or to the top of the Sannoisian. Dr. P. Oppenheim 3 has since re- 

 affirmed his acceptance of the Eocene age of the Fayum beds, and 

 says that they are at the highest, Ludian, that is, Priabonian. 



If Dr. Andrews's and Dr. Oppenheim's conclusions be correct, 

 then the marine deposits ended in Egypt at the close of the Middle 

 Eocene or Parisian (Lutetian), while the sea still covered Cyrenaica, 

 which only emerged in the Lower Oligocene. But, if Prof. Deperet 

 be right, the gap in the marine succession of deposits in Cyrenaica 

 occurred at the same time as in Egypt. 



1 0. W. Andrews, 'A Descriptive Catalogue of the Tertiary Vertebrata of 

 the Fayum, Egypt' British Museum, 1906, pp. ix, x. 



2 Ch. Deperet, ' Sur 1'Age cles Couches a Palceomastodon du Fayoum ' Bull. 

 Soc. Geol. France, ser. 4, vol. vii (1907) pp. 193-94 ; also ibid. pp. 455-56. 



3 P. Oppenheim, ' Observations sur TAge des Couches a Patcsomastodou du 

 Fayoum ' Bull. Soc. Geol. France, ser. 4, vol. vii (1907) pp. 358-60. 



