Dr. W. F. Rumc — GeoJotjn of Eastern Sinai. 203 



evidently of okler date, the coral having undergone much alteration 

 and being now of a dirty brown colour, though still in large measure 

 possessing the cavernous character of a modern reef. The fauna of 

 these beds has not yet been fully studied, but there is sufficient 

 evidence to show that we have here a remarkable combination of 

 Pectens of older aspect and Mediterranean character, associated with 

 modern Erythraean species similar to that revealed by a study of 

 Mr. Barron's collection of shells from the older reef on the west 

 side of the Eed Sea (see R. Bullen Newton, Geol. Mag., Dec. IV, 

 Vol. VII, pp. 500-514 and 544-560, Nov.-Dec, 1900). Thus, in 

 one bed of this series, Pecten Vasseli, Fuchs, and Chlamys latissima, 

 Brocchi, are associated in the same bed as Echinus verruculatus, 

 previously only recorded from Mauritius (identified by Dr. Gregory). 

 South of Sherm there is a tilted series of coral-reefs, rising nearly 

 200 metres above sea-level, whose fauna, although very obscure, is 

 probably very early Pleistocene, judging frona similar beds occurring 

 on the west side of the Gulf of Suez. It is of special interest to 

 note that these older reefs are only present at the southern end of 

 the Gulf of Akaba. 



After maintaining the general proposition that the coral-reefs 

 here are formed in a region of elevation, the question is raised (on 

 the ground of the observation made by Walther that an apparently 

 dead coral-reef was present metres below the present one), 

 whether this elevation is being continued, and it is pointed out 

 that the formation of bays at the mouths of several of the principal 

 valleys suggests that a small local depression is at present taking 

 place in the Gulf of Akaba, which thus differs from neighbouring 

 regions. The writer then considers the series of questions which 

 Professor Walther set himself to answer in his " Die Korallenriffe 

 der Sinai-halbinsel," and agrees with him — (1) that a coral-reef 

 (sensu stricto) does not attain any great thickness ; (2) as to the 

 role which detrital materials play in filling up a coral-reef; and 

 (3) the passage of coi'al limestone to dolomite by the increase of 

 magnesia. On the other hand, he has been unable to accept 

 Walther's view as to the basis of a coral-reef, the latter laying 

 stress on the importance of compact sedimentary rocks as a base 

 compared with igneous rocks, while in the paper under discussion, 

 after pointing out that the fringing reef of the Gulf of Akaba is 

 largely founded on igneous or metamorphic rock, the writer main- 

 tains that the deposition of a coral-reef is practically independent of 

 the nature of the rock forming its base, red granite, diabase, sand- 

 rock, and marls (probably also gneiss and hornblende - granite) 

 having been noted as its basal members. 



III. Cenomanian Limestones ; IV. Nubian Sandstone. — This is 

 a description of the relations and characters of the strata at the 

 northern end of the area examined, limestones forming the main 

 escarpment of Jebel Gunnah overlying a highlj'^ characteristic striped 

 series of green marls containing such typical Cenomanian fossils 

 as Hemiaster cnhicus, Pseudodiadema variolare, and Heterodiadema 

 libycum. These marls are themselves only the surface capping of 



