KAVIEONDO POTTO 
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river hog elsewhere. Although originally discovered on the 
eastern side, the great black forest hog ( Rylochcerus ) soon after 
turned up in the Cameroons ; and there is a possibility of the 
range of the okapi extending further west than is at present 
known to be the case. Amongst smaller mammals, the so- 
called African flying squirrels, better designated scale-tails 
(Anomaluridce), the pigmy squirrels of the genus Nannosciurus, 
and the civets of the genus Nandinia all have representatives 
on the eastern as well as on the western side of the forest tract, 
although the beautifully coloured Poiana, the African form 
of the Indo-Malay linsangs ( Linsanga ), appears to be restricted 
to the West Coast. 
‘ That the greater portion of the western fauna would even- 
tually be found to range over a large extent of the forest region 
was long ago predicted by Dr. A. R. Wallace in his Geograph- 
ical Distribution of Animals, where, however, the terms Western 
fauna and Western sub-region were still applied to the whole 
area and its animals. The time, as already stated, has now come 
when these terms should be replaced by the designations 
Forest fauna and Forest sub -region. That the fauna of the 
forest tract of Africa is intimately related to those of Ceylon, 
Southern India, and the Malay countries has been long familiar 
to naturalists, but it is only recently that an adequate and 
convincing explanation of the fact has been given to the world. 
For this we are indebted to Dr. Arldt, who points out that when 
the Siwalik fauna migrated from India to Africa, as it certainly 
did during later Pliocene time, probably by way of Baluchistan, 
Persia, and Arabia, or perhaps by a submerged line now re- 
presented by Socotra, the line of march must have been along 
a forest tract, as otherwise animals like chimpanzees and okapis 
Gould not have formed part of the company, and of these ancient 
forests we have evidence in the silicified tree trunks of the 
Punjab, Baluchistan, Syria, and Egypt. As the result probably 
of secular desiccation, the country subsequently assumed a more 
or less desert character, with the result that the forest animals 
were compelled to retreat to districts suitable to their habits ; 
in other words, to Ceylon, Malaya, and the equatorial forests of 
Africa. In this way, and in this way only, can be satisfactorily 
explained the fact that pigmy squirrels and chevrotains are 
