THE DESICCATION OF AFEICA 
151 
marshes which lie between Mweru and Tanganyika and run 
northwards. 
Of the Luvna I know little. There are vast sheets of open 
water and reed marshes along its course, linked up in endless 
ramifications, as occurs elsewhere in this region of Congo 
head- waters. Such abundance of water can hardly be included 
under the heading — desiccation. 
In reviewing the foregoing facts, the inland plateau of 
Africa, up to the Equator, can be roughly divided into three 
lateral zones : — 
1. From about the latitude of the Orange river to the 
Zambesi, where vast rivers and lakes have disappeared, leaving 
mere remnants, such as Lake Ngami. 
2. From the Zambesi to the latitude of Lake Mweru, where 
large river systems and huge lake areas are in process of being 
drained. 
8. The Equatorial belt, excluding Tanganyika, where the 
climate, rainfall, and vegetation is such, together with abund- 
ance of water, as to warrant the supposition that drainage 
and desiccation have not yet commenced. 
With the aid of geology and palaeontology, a fourth zone 
can be investigated in the north of Cape Colony and south of 
Orange Free State, where a semi-fossil form of Cobus has been 
found (cannot name exact locality without my notes). This 
form of Cobus is regarded as intermediate between the highly 
specialised, long-hoofed and water-loving C. lechwe and C. 
ellipsiprymnus. ( Vide ‘ Animals of Capetown Museum and 
South African Geological Society.’) 
The Loangwa Valley is worthy of special attention. Drainage 
evidently took place here on a large scale, and at a time when 
the lake areas were fully inundated and were impassable 
barriers to certain dry land fauna, such as Giraffe, Suni ( Neo- 
tragus ), and Spiny Mice (Acomys) (to mention extremes in 
size), on their migration to South Africa. 
Take Giraffe ; it is a native of North and East Africa down 
to German territory. It is also a native of South Africa. 
In the Loangwa Valley there was one known herd of some 
dozen animals in 1908. I knew this herd, which was pro- 
