THE TANGANYIKA PROBLEM. 127 



Passing north from Nyassa, we find that, with the 

 exception of the small crater pools occupying extinct cones 

 which occur along the continuation of the lake's valley 

 towards Rukwa, there are encountered no fresh waters of 

 any dimensions until we reach Kela, a small, nearly circular, 

 mere, with practically no fauna at all in it, beyond some 

 siluroid fishes and swarms of a minute species of Bithynia. 

 Curiously enough, Kela is within 20 miles of Tanganyika, 

 and yet there is not a single specific identity between the 

 fauna characteristic of the two lakes. Far to the east of 

 Kela lies the larger lake Rukwa ; it is a shallow sheet of 

 water occupying the floor of a continuation of the Nyassa 

 valley. Our most definite information respecting this lake 

 is that obtained by Mr. Wallace,* who, in 1897, made an 

 extensive geographical examination of the region, but who 

 observed nothing but minute shells, probably those of 

 Bithynia, and a number of siluroid fishes. f Far to the 

 west, again, we have the shallow and extensive expanse of 

 water which constitutes Lake Bangweolo. This lake is 

 known to contain siluroid fishes, but Mr. Weatherley 

 reports that it is "absolutely shell-less." Somewhat further 

 to the north lies Lake Mwero, a deep lake lying in a 

 secondary fold similar to that of Lake Rukwa, to the east 

 of Tanganyika. It has a much more profuse fauna than 

 either Rukwa, Bangweolo, or Kela. Among the fishes 

 occurring in Mwero, there have been recorded the following 

 fourteen different types : — 



* Journal of the Royal Geographical Society, 1897. 



t I believe some further information respecting the fauna of Lake Rukwa has more 

 recently been obtained by Dr. Ftilleborn, but no account of this appears yet to have 

 been published. See Chapter IV., p. 73, of present work. 



