142 MOSTLY MAMMALS 
Congo and the Nile in the neighbourhood of Wadelai. As 
a large number of the peculiar animals of this district are 
more or less exclusively confined to the west coast, extend- 
ing from Sierra Leone to the Congo, the area is appropriately 
termed the West African sub-region. It is here alone that 
we find the gorilla and the chimpanzee, the former being 
restricted to the neighbourhood of the coast, whereas the 
latter ranges far into the heart of the continent. And this 
district is likewise the exclusive home of the pretty little 
mangabeys, or monkeys with white eyelids (Cercocebus). 
The galagos, which are near relatives of some of the 
lemurs of Madagascar, extend throughout the forest region ; 
but the even more curious pottos, or thumbless lemurs, are 
confined to the west coast. Huge and forbidding fox-bats, 
some of them with remarkable tufts of long white hairs on 
the shoulders, are likewise restricted to this portion of the 
tract, as is the insectivorous otter, or Potamogale, first 
_ discovered during the travels of Du Chaillu. The equatorial 
forest-tract is also the sole habitat of the African flying- 
squirrels, to which further reference is made in the sequel ; 
all these being distinguished from the flying-squirrels of Asia 
by the presence of a number of scales on the under-surface 
of the tail. Most of them belong to the genus Anomalurus, 
but the smallest of all forms a genus (Jdiurus) by itself, 
while a flightless type (Zenkerella) also belongs to the 
group. Dormice of peculiar types and tree-mice are also 
very characteristic of this tract. But far more generally 
interesting are the pigmy hippopotamus of Liberia and the 
water-chevrotain (Dorcatherium) of the west coast, the latter 
an ally of the chevrotains of India and the Malay countries. 
So far, indeed, as the equatorial forest tract fauna has any 
representative in other parts of the world, it is to the 
Malay Peninsula and its islands that the resemblance is 
