Vol. 56.] FOSSIL CORALS AND ECHLNIDS OF SOMALILAND. 45 



Fig. 11. Metethmos asymmetrica, sp. nov. Dobar Limestone, Dobar. Coll. 



Mrs. Lort Phillips, a = side view ; b = horizontal section, both nat. 



size. (See p. 36.) 

 12. Litharcea Coles, sp. nov. Uradu Limestone, Uradu. ColL Mrs. Lort 



Phillips, a = part of the upper surface, X 2 diam. ; b = a horizontal 



section of the same, X 6 diam. (See p. 37.) 

 Figs. 13 & 14. Litharcsa Parkinsoni, sp. nov. Oherty Limestone, Somali 



Plateau. Coll. Mr. F. B. Parkinson. Fig. 13 = part of the surface, 



X 2 diam. ; fig. 14 = section across one corallite of another specimen, 



X t> diam. (See p. 37.) 



Discussion. 



Dr. Blanford said that a slight acquaintance with the geology of 

 a tract of country 500 miles away from Somaliland was scarcely 

 sufficient to justify him in commenting on this paper, which was a 

 valuable addition to our geological knowledge of North-eastern 

 Africa. The Author was probably right in regarding the Gulf of 

 Aden as of post-Eocene origin, but the evidence adduced of the 

 post-Eocene elevation of the Somali plateau did not absolutely 

 preclude the possibility that the depression forming the present 

 Gulf of Aden existed earlier. The opening of the Straits of Bab- 

 el-Mandeb appeared to be of very late geological date, perhaps 

 Pleistocene. 



Mr. Walcot Gibson said he was sure that all interested in African 

 geology would be indebted to the Author for bringing to our 

 notice the existence of Lower Tertiary beds with a Tertiary fauna 

 on the plateau of Somaliland. A few undoubted facts fixing the 

 age of sediments in East Africa are exceedingly welcome. 



Mr. G. C. Crick asked the Author whether the Pseudodiadema 

 from Bihin threw any light on the age of the Bihin limestone, as 

 the cephalopoda from the same locality appeared to indicate the 

 presence of an horizon somewhat younger than Bathonian. 



The Author, in reply, said that he thought the Pseudodiadema 

 gave no more precise information as to the age of the Bihin lime- 

 stone than that it was approximately Callovian or Bathonian. The 

 only Tertiary marine fossils from the Erythraean Rift- valley of which 

 he knew were a doubtful echinid from Nyasaland, and the Miocene 

 fossils from the northern part of the Red Sea. The absence of 

 Kainozoic marine deposits, except Pleistocene, in the southern part 

 of the Bed Sea, and the fact that those of the northern part of that 

 area are of the Mediterranean, and not of the Indian Ocean type, 

 rendered it probable that the Aden Gulf was formed by the same 

 series of movements as those which formed the Somali scarp. 



