226 PROF. J. W. GEEGOEY ON NEPHELINE-SYEISTTE [May I9OO, 



that district occur on the mainland opposite Mombasa, where they may 

 be seen in the bed of the estuary west of Freretown, on the slopes of 

 the three hills known as the Qoroa Mombasa, and opposite Mombasa 

 on the main slope from Makupe Ferry up to Changamwe. The beds 

 are a series of iron-stained shales, with lines of ironstone-nodules, 

 the whole dipping eastward. Thence I collected a number of 

 cephalopods which Mr. G. C. Crick, of the Natural History Museum, 

 has kindly undertaken to describe. The fauna shows that the beds 

 at this locality (as previously held by Futterer 1 ), are mainly of 

 Kimeridgian age, from the zone of Aspidoceras acantliicum. 



South of tin's point fossiliferous Jurassic rocks reappear near 

 Tanga, Saadani and Mtaru, where the fossils, as described by Futterer, 

 Jaekel, and Tornquist, show that the beds are of Middle Jurassic age, 

 being Oxfordian and Callovian. 



Immediately to the west of this belt of Upper and Middle Jurassic 

 rocks is a great series of sandstones, which appear to reach their 

 highest development in the Shiniba Mountains. Baron Stromer 

 von Reichenbach has proposed for them the convenient name of 

 Duruma Sandstones. Hildebrandt clearly regarded these beds 

 as older than the Jurassic, for they are described in Beyrich's paper 2 

 as extending from the Jura-formation to the Archaean Series. 



But this view has not been always accepted. In an account of 

 the geology of Usambara, the country immediately south of the 

 Anglo-German boundary, and of the district west of Bagamoyo, in 

 both of which the geological sequence is similar to that near Mombasa, 

 Joseph Thomson claimed the whole series between the Archaean 

 and the Pleistocene (which I presume covers his Tertiary) as Car- 

 boniferous. This conclusion was apparently based on his own iden- 

 tification of some fossils Avhich he thus describes 3 : — 'The contained 

 fossils, such as corals and marine shells, were, as far as seen, in too 

 imperfect a state of preservation to be recognizable, and my short 

 search did not enable me to secure any specimens capable of deter- 

 mination, although I have no doubt that a more careful examination 

 will bring to light many good fossils.' A subsequent reference to 

 these fossils in 1881 is more important, as he then mentions an 

 exact locality 4 : — ' At Umba, in Usambara, I found one bed of 

 limestone with numerous fossils of characteristic Carboniferous 

 types.' 



Baron Stromer von Reichenbach 5 has already thrown doubt on 

 this identification, and I am not aware that any fossils from Umba 

 have been definitely determined. The Rev. J. P. Farler 6 has briefly 

 described the lithological character of the rocks near Umba, and 



1 ' Beitrage zur Kenntniss des Jura in Ost-Afrika ' Zeitschr. Deutsch. Geol. 

 Gesellsch. vol. xlvi (1894) pp. 2-15 & 49. 



2 Monatsber. k. Preuss. Akad. Wissensch. Berlin (1878) p. 774. 



3 'Notes on the Geology of Usambara' Proc. Roy. Geogr. Soc. n. s. vol. i 

 (1879) p. 560. 



4 ' To the African Lakes and Back ' vol. ii (1881) p. 301. 



5 'Geologie d. deutscben Schutzgebiete in Afrika ' Munich, 1896, p. 24. 



6 ' The Usambara Country in East Africa ' Proc. Roy. Geogr. Soc. n. s. vol. i 

 (1879) p. 87. 



