■28 



DR. J. W. GREGORY ON THE GEOLOGY AND [Feb. I9OO, 



were collected by Prof. Keller on the south-western slopes of the 

 Somali plateau, along the valley of the Eaf, a tributary of the Webi 

 Shebeli. 



A geological collection made in the winter of 1894-95 by Mr. and 

 Mrs. Lort Phillips, Miss Edith Cole, and Mr. G. P. V. Aylmer demon- 

 strated the occurrence of two distinct limestones in the central area 

 of the Guban, south of Berbera. 1 In the paper describing this 

 collection, some suggestions were made as to points on which 

 information would be especially useful ; and in reply I have received 

 some further collections which practically settle the three problems 

 then mentioned as unsolved. The largest collection was made by 

 Mr. and Mrs. Lort Phillips, Miss Gillett, and Mr. G. P. Y. Aylmer 

 in the Golis Mountains and in the coastal belt between the foot of 

 the Golis scarp and the sea. Capt. E. T. Marshall has kindly sent 

 me a supplementary collection of rocks from the Haud and of 

 fossils from the raised beaches of the Maritime Plain. A collection 

 of fossils from the limestones east of the Berbera district and some 

 fossils from the high-level limestones has been made by Mr. P. B. 

 Parkinson. To Mr. Aylmer I am greatly indebted for a carefully- 

 prepared map of the Guban and of the watershed along part of the 

 northern margiu of the central plateau. 



To all these travellers I must express my best thanks for their 

 interesting collections, which throw light on three problems : — the 

 distribution of the Archaean rocks ; the age and sequence of the 

 limestones ; and the dnte of the foundering of the Aden Gulf. 



II. The Arch.3ean Series. 



The Archaean rocks from the Haud and its northern outliers 

 include gneiss, ainphibolites, mica- and chlorite-schists, coarse quartz- 

 orthoclase-pegmatites, etc. They belong to types familiar from the 

 descriptions of the similar rocks from Socotra by Prof. Bonney a and 

 from Western Somaliland by Miss Raisin. 3 



The principal varieties have been recorded from the area south of 

 Berbera in my note of 1896 (op. jam cit.). It is therefore only 

 necessary to give the following list of localities where the present 

 collections have proved the occurrence of the Archaean Series : — 



Localities. 



.V. Lat. 



E. Long. 



District. 



Altitudes 

 in feet. 





East of Gellakur . . . 



10° 5' 



45° 15' 



Uradu 





Syenitic gneiss. 



Foot of Rugga Pass 



10 



45 20 



,, 





Gneiss. 



Top of Rugga Pass 



10 



45 20 



Golis 



4300 



Gneiss and quartzite. 



Upper Sheikh 



9 55 



45 10 



!> 



4543 



Gneiss and chloritic 

 schist. 



Sok Soddah 



9 47 



45 20 





4308 



Saussuritic gneiss and 

 chloritic schist. 













1 See rnv ' Note on the Geol. of Somaliland/ Geol. Mag. 1896, pp. 289-94. 



2 T. G.' Bonney. 'Coll. Rock-specims. fr. I. of Socotra,' Phil. Trans. Roy. 

 Soc. vol. clxxiv (1883) pp. 273-94 & pis. vi-vii. 



3 C. A. Raisin, ' Rock-specirns. fr. Somaliland ' Geol. Mag. 1888, pp. 414-18. 



