578 THE GEOLOGY OF CYRENAICA. [NOV. 19II. 



and the benefit of their indefatigable co-operation. They collected 

 many of the fossils, and to Mr. Duff is due the map of our route, 1 on 

 which the geological map (PI. XLII, fig. 1) is based. I have also to 

 express my thanks to Mr. Justin C. W. Alvarez, our Consul-General 

 at Tripoli, and to Messrs. R. A. Fontana and G. Farrugia, the 

 British Consuls at Benghazi and Derna, and to M. Jacoub Krieger, 

 the confidential secretary to the late Redjeb Pasha, for his unfailing 

 courtesy and help. 



I am greatly indebted to Mr. R. B. Newton for the care with 

 which he has studied the fossil mollusca collected by the expe- 

 dition, and the accompanying memoir on them. I am also indebted 

 to Mr. P. Chapman for his report on the foraminifera, and to 

 Mr. D. P. Macdonald for his careful microscopic examination of the 

 limestones. Dr. C. W. Andrews has kindly helped me with reference 

 to the literature on the fossil mammalia of the adjacent areas. 



The magnetic variation in Cyrenaica was taken as 6° W. 



Por the literature on Cyrenaica, reference may be made to two 

 chief bibliographies — P. L. Playfair, ' The Bibliography of the 

 Barbary States: Part I, Tripoli & the Cyrenaica' Boy. Geogr. 

 Soc, Supplementary Papers, vol. ii, pt. 4 (1889) pp. 559-614 ; 

 and G. Hildebrand, ' Cyrenai'ka als Gebiet kiinftiger Besiedelung ? 

 Bonn, 1904, pp. 329-78. 



II. Pield-Observations. 



(a) The Neighbourhood of Derna. 



Derna is situated on a delta-fan of limestone-gravel at the mouth 

 of the Wadi Derna. The gardens in the town are irrigated by 

 water from springs at Seghia and Boninansur, respectively about 

 4 and h\ miles up the wadi. The river-bed is covered by coarse 

 limestone-shingle, and is usually waterless. It forms, in fact, the 

 main thoroughfare through the town. Above Derna the river 

 emerges from a deep gorge, and near its mouth is a bank of tufa, 

 which rises to the height of 100 feet up the eastern side of 

 the wadi : it consists of successive layers of calcareous sand, 

 of tufa largely composed of cylindrical fragments, and of rolled 

 limestone boulders. This deposit obviously represented a delta-fan 

 which had been formed at the mouth of the wadi, before the gorge 

 had been corroded to its base-level. The material was due to the 

 alternate deposition of coarse shingle during floods, and of tufa 

 during intervals when the only water came from adjacent springs. 



The sections along the Wadi Derna expose two main rocks : the 

 lower part of the cliffs consists of a soft white to cream-coloured 

 limestone, crowded with large flat nummulites, and similar to the 

 typical JNummulitic Limestones of the Mokattam Series of Egypt. 



According to Mr. Chapman, the foraminifera, which are unusually 

 well preserved, are of Middle Eocene age. The most characteristic 



1 [A MS. copy of the map will be placed in the Society's Library.] 



