Miss C. A. Raisin—Rocks from Somali Land. 417 
(4.) Quartzite—This is formed of very well rounded grains 
cemented by crystalline silica, and is thus similar to the specimen 
recently described by Professor Bonney from near Ightham.' The 
cement consists mainly of crystals projecting outwards, and ranged 
in successive layers, which are separated by dusty lines. Tho 
wider interstices are filled in, towards the interior, by clear chalce- 
donic granules, the depusit being sometimes completed in the centre 
by a brown opaque material. The grains of the quartzite are mostly 
simple, but sometimes composite, and they contain rutile-like 
needles, and lines of cavities with moving bubbles. The quartz 
may appear very dirty, or it may contain only few enclosures, but 
in several examples these cease along a narrow marginal zone, 
which, therefore, probably represents siliceous cement deposited in 
crystalline continuity with the original grains. 
Sedimentary Rocks. 1. Grits and Sandstones.—One specimen of 
sand, which consists of well rounded grains, is labelled ‘‘ red earth 
used for dyeing.” The quartz grains are large, and are coated 
with ferruginous deposit, and seem thus not unlike the red sands 
of the Arabian Desert described by Mr. Phillips.» Fragments 
which are more angular form the constituents of a coarse, claret- 
coloured grit, and of a very strong brown sandstone, which was 
obtained from Mount Hilo, and is probably the one mentioned as 
suitable for grindstones. In all the sands and grits, the quartz is 
more or less coated with a ferruginous substance, which is not un- 
frequently a kind of pisolitic deposit, similar to that described in the 
granite. In some of the specimens there are quartz pyramids con- 
nected with the grains, which recall the appearance of the additive 
crystals figured by Mr. Phillips. Besides quartz, the slides contain 
fragmental felspar, often plagioclase, also films of brown mica, and 
occasionally a hornblende or tourmaline fragment or a garnet. 
2. Limestones.—The lithographic stones, as well as other of the 
limestones, have a very compact character, as is illustrated also by 
a specimen from the floor of Hilo cave, “ polished by the passage of 
animals over it.” (1.) From Mount Hilo. This pale buff-coloured 
limestone is as compact in character, but has the appearance of a 
fissile structure. It is in a partially crystalline condition, but with 
much admixture of earthy material. This limestone, and some of 
the lithographic stone with most marked conchoidal fracture, yielded 
only slight traces of fossils, but in slides prepared from two speci- 
mens, organic remains were well able to be identified, although they 
were less clear in one of the two rocks, which appeared to have 
undergone greater dolomitization. These slides, with my conjec- 
tures as to the identification of the fossil forms, were submitted to 
Prof. Rupert Jones, and the following isa list modified in accordance 
with the opinion he kindly expressed. 
(2.) Limestone, fourteen miles south of Bulhar. This contains 
1 Grot. Mac. July, 1888, Figure on p. 299. 
2 QJ.G.S. 1882, vol. xxxviii. p. 111. 
> Q.J.G.S. 1881, vol. xxvii. ‘ On the Constitution of Grits and Sandstones,”’ 
pl. i. figs. 1, 2, 3, 5. 
DECADE III.—vVoOL. V.—NO. IX. 27 
