262 ZOOLOGICAL GEOGRAPHY. [part hi. 



zoology, though there is reason to believe that it is a compara- 

 tively recent intruder into the country. 



II. The West-African Sub-region. 



This may be defined as the equatorial-forest sub-region, since it 

 comprises all that portion of Africa, from the west coast inland, 

 over which the great equatorial forests prevail more or less unin- 

 terruptedly. These commence to the south of the Gambia Eiver, 

 and extend eastwards in a line roughly parallel to the southern 

 margin of the great desert, as far as the sources of the upper 

 Nile and the mountains forming the western boundary of the 

 basin of the great lakes ; and southward to that high but marshy 

 forest-country in which Livingstone was travelling at the time 

 of his death. Its southern limits are undetermined, but are pro- 

 bably somewhere about the parallel of 11° S. Latitude. 1 



This extensive and luxuriant district has only been explored 

 zoologically in the neighbourhood of the West coast. Much, no 

 doubt, remains to be done in the interior, yet its main features 

 are sufficiently well known, and most of its characteristic types 

 of animal life have, no doubt, been discovered, 



Mammalia. — Several very important groups of mammals are 

 peculiar to this sub-region. Most prominent are the great 

 anthropoid apes — the gorilla and the chimpanzee— forming the 

 genus Troglodytes ; and monkeys of the genera Myiopithecus 

 and Cercocebus. Two remarkable forms of lemurs, Perodicticus 

 and Arctocebus, are also peculiar to West Africa. Among the 

 Insectivora is Potamogale, a semi-aquatic animal, forming a 

 distinct family ; and three peculiar genera of civets ( Viverridaa) 

 have been described. Hyomoschus, a small, deer-like animal, 

 belongs to the Tragulidse, or chevrotains, a family otherwise 



1 Dr. Schweinfurth has accurately determined the limits of the suh-region 

 at the point where he crossed the watershed between the Nile tributaries and 

 those of the Shari, in 4^° N. Lat. and 28£° E. Long. He describes a sudden 

 change in the character of the vegetation, which to the southward of this 

 point assumes a West-African character. Here also the chimpanzee and 

 grey parrot first appear, and certain species of plants only known elsewhere 

 in Western Africa. 



