THE TANGANYIKA PROBLEM. 
343 
the greater number of the species of the Mormyridse are 
endemic in the Congo. 
On the whole, then, these facts appear to indicate that 
Tanganyika was originally stocked with halolimnic animals 
from a western sea, of which the great lake itself, and the 
vast back-waters of the Congo, may be said to be the last 
remains. From these regions, those fishes which were able 
to withstand the vicissitudes imposed by the physical 
changes which have brought about the modern appearance 
of the Continent, have wandered in all directions, varying 
Example of a typical Pyrgtilifera from the 
upper chalk of Ajka. From a specimen in the British Museum. 
as they went. But the bulk of the species of these fish are 
still found confined within this region even to the present 
day. 
It simply remains for us now, therefore, to ascertain 
whether there is anything in the nature of the halolimnic 
animals still surviving in Tanganyika, which will enable us 
to determine to what age and type of sea-fauna they 
belong. 
It has been seen that one of the characteristic anatomical 
features of the animals belonging to the halolimnic group is, 
that they all possess characters which could be ascribed to 
the ancestors of numerous existing marine forms, or, in other 
