22 EINAE LONNBBRG, MAMMALS COLLECTED BY THE SWEDISH ZOOLOGICAL EXPEDITION ETC. 



uniform climate, and perennial luxuriance of vegetation » — — — ; 3:o the South 

 African to which belonged the » extra-tropical » southern portion of the continent. 

 The boundary-lines need not to be quoted, they have of course had to be altered, 

 because at the time when Wallace wrote this the knowledge of the interior of Africa 

 was, as he points out himself, imperfect. 



The chief interest with this division is that Wallace on the base of as well 

 physical as biological conditions forms the East- and West African subregions, the 

 » extra- tropicals has subsequently proved less important. Heilpkin divided^ also 

 »the Ethiopian Realm* in three subregions which he named the » East-Central Afri- 

 can*, the »West Africans and the »Saharan». The first of these included also South 

 Africa, and the last, the northern desert country, the fauna of which nvith almost 

 insensible gradations, merges into the fauna of the Mediterranean transition tract ». 



Lydekker prefers Heilpbin's subdivision but adds that Somaliland probably 

 ought to be regarded as a separate subregion. 



In a book entitled »The Geography of Mammals» W. L. and P. L. Sclater 

 in the year 1899 used a zoogegraphical subdivision of the Ethiopian continent which 

 is intermediate between Wallace's and Heilprin's systems. They have l:o »the 

 West African subregion, including the great equatorial forest of Central Africa con- 

 tained in the basins of the western rivers, from the Senegal to the Congo inclusive*; 

 2:o »the Cape subregion including all Africa south of the watershed of the Congo 

 on the West and of the Tana on the East coast*; 3:o »the Saharan subregion, 

 consisting (if we exclude the Abyssinian plateau) chiefly of desert, or at any rate 

 of a comparalively dry country, including the Sahara, Eastern Africa as far south 

 as the Tana river, and Southern Arabia. » 



In this division as well due regard is taken to the physical and biological 

 conditions of the three subregions. The characteristic features of the landscape of 

 these subregions are just those three original types of African landscape which have 

 been mentioned above viz. forest, steppe, and thornbush resp. desert. 



It appears also evident that certain faunistic elements are more or less strictly 

 bound to one or the other of these types of landscape. But not all mammals by 

 far are so dependent on the environment. Many strong or adaptive mammals may 

 occur in two, and some even in all three of these kinds of landscape. Steppe and 

 thornbush are, however, more alike than either with the forest, and the faunas of 

 the two former have therefore a greater number of elements in common than either 

 of them have with the forest. 



The three geographical subregions as defined by the Messrs. Sclater are, 

 however, not homogenous. There are forests outside the »West African subregion*, 

 there is open country outside the *Cape Subregion », and so on. These outlying 

 portions of landscape, otherwise typical to anoter zoogeographical subregion, must, 

 however, be taken in possession by some kind of animals to which they offer suitable 

 conditions of life (whether this primarily or secondarily is the case). Now it depends 



^ The Geographical and geological Distribution of Animals. Eded. 1894. 

 ^ Die geograph. Verbreitung u. geolog. Entwickelung der Saugetiere 1897. 



