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



Affinities. — The main characters of this species are the absence 

 of tubercles in the ambulacra, and the occurrence there of four to 

 five rows of granules. It belongs to the same group of species as 

 the Bajocian Ps. Jauberti, Cott. 1 in which, however, the pore-pairs 

 are not doubled near the peristome. Ps. muelense, P. de Lor. 2 from 

 the Sinemurian of Portugal, agrees in the extensive ornamentation 

 of the interambulacral plates ; but though its ambnlacral tubercles 

 are small, they are much larger than in Ps. soma! 



? CONOCLYPEUS, sp. 



In Mr. F. B. Parkinson's collection there is a large flat echinid of 

 which the base is all but lost. Its generic determination is there- 

 fore impossible, but it may be useful to record the specimen for 

 reference, in case other imperfect specimens should be found. The 

 specimen came from a massive limestone, which is no doubt Eocene, 

 as Mr. C. D. Sherborn and Mr. F. Chapman hare kindly identified 

 some forammifera in the matrix as JSummuUtes sp., Amphistegina 

 sp., and Orbitoides dispansa (Sow.). 



The specimen came from the beds of limestone associated with 

 gypsum on the Somali plateau. The exact locality is apparently 

 Kirrit (lat. 9° N. and long. 46° 10' E.), south of Bur Dab. 



VI. The Limestone Sequence and the Date of the Foundering 

 of the Aden (julf. 



The palocontological evidence at present available shows that the 

 limestones of Somaliland belong to five different ages — Lower 

 Jurassic, Neocomian, Turonian (? Cenomanian), Eocene, and 

 Pleistocene. 



The oldest of the five limestones occurs at Bihendula, near 

 the foot of the plateau-scarp, some 20 miles south of Berbera. 

 Mrs. Lort Phillips collected four species of fossils from this locality 

 in 1894-95. They were two species of brachiopoda, determined by 

 Mr. F. A. Bather as IVujnchonella Edwardsi, Chapuis & Dewalque, 

 and lib. subtetrahedra, Dav. ; a lamellibranch identified by Mr. R. B. 

 Xewton 3 as Parallelodon Egertonianus, Stoliczka ; and a belemnite, 

 recorded by Mr. G. C. Crick 4 as B. subhastatus, Zieten. The Bihendula 

 Limestone was accordingly determined as of Lower Jurassic, and 

 probably of Bathonian age. The belemnite is characteristic in 

 India of the macrocephalus-zone, the lowest part of the Callovian ; 

 Mr. Crick distinguished it from B. tanganensis, Futterer, of the 

 Lower Oxfordian of East Africa, and suggested that it might be 

 identical with the fossil from Shoa, identified by H. DouvilleP as 



1 G. Cotteau, 'Echinides Keguliers,' Pal. franc,-. Terr. Jur. vol. x, pt. ii 

 (1881) p. 238 & pi. cccxxiii, figs. 6-14. 



- P. de Loriol, ' Descr. Faune Jur. Portugal, Embr. des Echinod.' pt. i 

 (1890) p. 82 & pi. xv, figs. 1-5. 



3 K. B. Newton, ' Oecurr. of an Indian Jur. Shell in Somaliland ' Geol. 

 Mag. 1896, pp. 294-96. 



4 G. C. Crick, ' Fragm. of Belemn. fr. Somaliland ' ibid. pp. 296-98. 



5 H. Douville, ' Foss. rapp. du Choa par M. Aubry ' Bull. Soc. geol. France, 

 ser. 3, vol. xiv (1886) p. 223. 



