o70 REPORT OF THE HARVARD AFRICAN EXPEDITION 
No doubt a number of other Liberian mammals may be added to this list when 
our knowledge of their exact relationships is complete. We are describing also a 
local form of the short-haired bush-rat, Hylomyscus. 
In addition to these species that are represented in the Liberian and adjacent 
forest areas by races distinct from their representatives in the Cameroons and 
Congo forests, there are a few which seem to be peculiar to the strip of heavily 
wooded country along the coasts of Sierra Leone and Liberia. Notable among 
these are the Pygmy Hippopotamus, Jentink’s Duiker, and the curious Zebra 
Antelope, which appear to be wholly confined to the densely wooded parts of these 
two countries. One may imagine their distribution to have once been wider when 
the forests extended farther inland and were broadly continuous with the Congo 
rain-forest and perhaps stretched to the east coast. There has probably been a 
long period of progressive drying out during and since Pleistocene times resulting 
in the development of the Sahara Desert and in the retreat of the forest toward 
the more rainy portions of the western coast. Here, north of the Bight of Biafra, 
these species have been more or less cut off from the great forest of the Congo 
basin, so that there has been no exchange of forest-living types between them. 
Of smaller species that seem in like manner to be peculiar to this coastal forest 
are: — 
Perodiclius potto Dephomys defua Hybomys trivirgatus 
Perhaps in part through this partial isolation from the larger forest area, there 
are a number of genera found in the Congo that apparently do not occur at all in 
the coast-forest extension from Gold Coast to Sierra Leone. Such are: the gorilla 
(Gorilla), Galago (unexpectedly), various small rodents as Stochomys, Oenomys, 
Colomys, Idiurus, Zenkerella, and such larger, hoofed mammals as the okapi 
(Okapia) and the forest pig (Hylochoerus). It is further interesting that the 
Liberian representatives of certain more widely-spread types are more primitive 
than those occurring outside this area. Thus the Pygmy Hippopotamus is a 
less specialized animal than its giant representative of other parts of Africa, 
while among the Colobus Monkeys, the extraordinary development of the 
white decorative fringes found in the central and eastern African species, is least 
marked in the Liberian C. polykomos. 
The list that follows is intended to include all species of mammals whose 
occurrence in Liberia has been authenticated. The list published by Jentink 
on the basis of Biittikofer’s work included ninety species to which Miller in 
1900 added nine. Subsequently, Johnston (1906) in his two-volume work on 
Liberia, gave a very good general account of the Liberian mammalian fauna, and 
added a list of one hundred three names, some of which, however, are obviously 
synonyms of other included species, while others still are given provisionally, on 
admittedly unsatisfactory evidence, as the Hedgehog, two Hyenas, Lion, Rhi- 
noceros, Forest Pig, all of which may eventually be found, particularly the first 
four, whose ranges may touch the eastern border of Liberia beyond the forest. 
Our list comprises one hundred one species, exclusive of the Cetacea, and of these, 
five (Crocidura nigricans, Petalia arge, Hipposideros langi, Anomalurella and 
Hylomyscus) are recorded for the first time from the Liberian area. The small 
