THE VICTORIA NYANZA 
5 
the lime-laden waters of the lagoon or shallow gulf of the 
Victoria Nyanza. It was succeeded by another well-marked 
torrential period, during which the river deposited coarse 
gravels (Nos. 26-29), with a calcareous cement, deriving their 
constituents from gneiss, andesite, jasper, and quartz, occurring 
in situ in the country 20 to 80 miles to the eastward, and 
especially derived from the volcanic agglomerate of Metamala. 
During the period represented by the Middle Series 
(Beds 18-25) the river-system was becoming mature, so that 
torrential beds were exceptional and temporary, and are 
confined to the lower half, whilst in the upper half red clays 
predominate, interrupted by occasional seams of travertine, 
often mixed with clay. A thin, orange gravel (No. 24) near 
the base of the series (Fig. 2) is of special importance on account 
of the number of teeth it contains, comprising those of Dino- 
therium, rodents (probably ancestral to the cane-rats), 
crocodiles, and of the lungfish Proto'pterus (hitherto unknown 
in a fossil condition). One of the white sandstones (No. 22) 
is so hard that the fossils it contains are exceptionally well 
preserved, in particular a Proboscidean tibia, perhaps of 
Dinotherium or Tetrabelodon, and a complete carapace of 
Trionyx. 
Intercalated among the upper red clays (Fig. 8) is a thin 
grey sandstone (No. 16), containing a few small jawbones 
which Dr. C. W. Andrews has determined to belong to a remark- 
able form, related to Hyrax, with some rat-like characteristics 
doubtless due to convergence. Still higher in the series a 
hard red marlstone (No. 14), often travertinous, contains 
abundant casts of the shells of Ampullaria ovata (with opercula) 
and Lanistes carinatus with fragmentary crocodilian and 
chelonian remains. This bed forms a remarkably persistent 
horizon and is readily recognisable from its tendency to form 
a wide terrace (as at Nira) and the edge of a cliff (Fig. 2). 
The red colour of this marlstone and of its associated clays 
(Nos. 13 and 15) diminishes towards the east and has become 
greenish-grey at Kikongo, five miles east of Nira. Their red- 
ness may perhaps indicate the activity of ferruginous springs 
at the time of deposition. Discontinuous layers of calcareous 
concretions occur in the clays and probably owe their irregular 
