﻿vol. 6 1.] cretaceous systems of the nile valley. 677 



Discussion. 



Capt. H. G. Lyons remarked on the interesting character of the 

 area described by the Author, situated as it was at the end of the 

 Nile- Valley faults. The more recent deposits referred to would 

 probably, when worked out in detail, throw valuable light on many 

 points connected with the history of the valley. The evidence of 

 a conformity between the Cretaceous and the Eocene strata was 

 most interesting, and would certainly necessitate some modification 

 of the views hitherto held concerning the area lying to the north. 

 Until further detailed examination had been made, he would prefer 

 to suspend judgment on the point, whether this conformity continued 

 as far as the Farafra Oasis, since in the Baharia Oasis, not 70 miles 

 farther north, the unconformity was most strongly marked. 



Mr. E,. Bullen Newton wished to state his position with 

 regard to the shell figured and described by himself in 1898, as 

 Pecten Mayer-Eymari, which had been alluded to by the Author. 

 This Egyptian shell was obtained from Eastern Desert and Nile- 

 Valley localities, being regarded by Messrs. Barron & Hume as 

 of Lower Eocene age. As its facies seemed to support this horizon, 

 it was so described. In 1900 Dr. Blanckenhorn, in his memoir 

 on the Eocene of Egypt, noted the fact that Pecten Mayer-Eymari 

 was synonymous with P. farafrensis of Zittel (1883), and 

 belonged to Upper Cretaceous rocks. At this date ZitteFs shell 

 was known only as a list-name, never having been figured or 

 described ; and it was not until 1902 that Dr. Wanner published its 

 details, and followed Dr. Blanckenhorn in placing P. Mayer-Eymari 

 in its synonymy. A subsequent study of examples of the so-called 

 P. farafrensis from the Libyan-Desert areas of Farafra and Baharia 

 had convinced the speaker that, allowing for a somewhat variable shell, 

 the two forms may be included under the same specific name, which, 

 on account of priority, must now be known as P. Mayer-Eymari, the 

 old name suggested by Zittel not being retainable. A further 

 palseontological investigation of the fauna associated with this shell 

 confirmed in every way Dr. Blanckenhorn's statement that it belongs 

 to Upper Cretaceous rocks and ranges from the Campanian to the 

 Danian : the Campanian forms being restricted to the Eastern Desert 

 and Nile- Valley localities, while the Danian are confined to the 

 Libyan Desert. Moreover, the Author had eliminated the theory 

 of an unconformity existing between these Pecten Mayer-Eymari 

 Beds and the rocks beneath, and so fully supported the view as to 

 the Cretaceous age of these deposits. 



The President said that he was glad to find that the Director of 

 the Geological Survey of Egypt agreed with the main conclusions of 

 the Author. With reference to an unconformity occurring at no 

 great distance from an area where the beds were conformable, he 

 thought that at least three such cases could be cited in the limited 

 area or* Great Britain. 



The Author, in reply, observed that the President's allusion 

 to similar cases of rapid change from conformity to unconformity 



