58 
THE TANGANYIKA PROBLEM. 
of our supposed boring. Where alluvium and lake deposit 
has accumulated in this manner in vast masses, as it has 
on the Shirwa plain, for example, and in the basin of 
Lake Pamalombi, there are, unfortunately, no very deep 
water cuttings to be found, and the examination of those 
which exist by Sir John Kirk, ourselves and others, have 
revealed nothing but the semi-fossilised remains of existing 
land animals, such as elephants, hippopotami, and the 
remains of fishes and fresh-water shells. In the case of 
the great Shirwa plain, however, these lake deposits and 
layers of terrestrial alluvium are, by whatever method we 
may estimate them, very thick, and their deposition must 
have gone on without break from a remote geological 
antiquity until the present day. It is, therefore, quite 
certain that deep excavation in such localities, or their 
examination in some favourable spots which have yet to 
be discovered, would reveal in their deeper portions animal 
remains which differ from those now inhabiting the African 
lakes and plains. There is no reason why such fiats as 
these occurring in the Shiri highlands should not contain 
zoological remains as different from the existing fauna, 
and as full of interest, as the remains recently obtained 
from the very similar fiats in Madagascar by Mr. Forsyth 
Major, and more recently from Fayum by Mr. Andrews. 
Passing to the west of the Shiri districts we find that in 
part of the Nyassa region proper, as I explained in the 
preceding chapter, the geological characters of the country 
throughout the whole district are very similar to those of the 
Shiri highlands ; granitoid ridges run north and south, and 
contain between them rock valleys which are often partially 
filled up with horizontal masses of old lake deposit and 
alluvium, these masses themselves representing the wear and 
tear of a country that has not changed much since the 
