FAUNA OF THE AFRTCAN LAKES. 



537 



Tanganyika, however, is the extreme case, where not merely 

 specific but generic distinctions occur, and a remai-kable fish fauna 

 exists which has very little in common with the fislies of the 

 Congo, and which, moreover, has no parallel elsewhere. 



Alberb Nyanz.i is the only lake of those under review which 

 does not contain a single endemic species of fish. The family 

 Siluridfe is best represented, with 7 different forms, belonging to 

 6 ditierent genera, but these are without exception well-known 

 Nilotic species. Very few Oichlid fishes are found in the lake, 

 the most interesting being Petrochromis andersoiiii, a Tanganyika 

 type, the existence of which in Lake Albert needs confirmation. 

 With this exception, and with the exception of Alestes macro- 

 phthahmis^ a Congo-Tanganyika type, the occurrence of which in 

 the lake is also rather doubtful, the whole of the fishes belong- 

 essentially to the Nile system, of which the lake is thus shown to 

 be an integral part. 



Lake Edward, which lies further south, but is similarly in 

 direct connection with the Nile, is nevertheless not without types 

 peculiar to itself. Two endemic speces of Barhus have been 

 described, and one of Clarias. The Cichlidae are well represented 

 here with 12 forms, 3 of which, including the genus Schubotzia, 

 are endemic. While the greater number of the fishes are either 

 Nilotic types or are peculiar to the lake, there is a series of 

 6 Uichlids which are common to Lakes Edward and Victoria, and 

 are not found elsewhere. This is a rather unexpected state of 

 a.ftairs, and it is by no means easy to account for the association, 

 since the lakes do not communicate in any way. It may be nofced 

 that in Lake Edward the total number of genera is reduced to 

 eight and the number of families to four. 



Dealing lastly with Lake Kivu, the smallest lake is seen to 

 contain the smallest number of dift'erent species of fish. Yet 

 even here an endemic species of Ba7'bus and two endemic Cicldids 

 occur. Apart from these, the fish fauna gives indications of 

 being considerably mixed. Three species belong clearly to the 

 Nile group, while reference has already been made to the two 

 forms of llai)lochromis found in Lakes Kivu and Edward only. 

 On the other hand, two fishes are found in Kivu and Tanganyika 

 onl}^ : a third occurs in Tanganyika and the Rusisi River which 

 drains Lake Kivu, as well as in the lake itself. The two remaining 

 types have a wider distribution, extending into W^est Africa. 



In works dealing with Geographical Distribution it has long- 

 been recognised that undoubted affinities exist between tlie 

 animals of Southern Asia — and of the Indian Peninsula in par- 

 ticular — and of East and Central Africa. While evidence of this 

 is more marked in .some groups than in others, clear testimony 

 as to the general truth of the assertion is to be gained by a study 

 of certain families of fishes. Of the families under discussion, 

 it is pre-eminently the Cyprinidae and Mastacembelidte which 

 exhibit this affinity in a striking degree. Among the Cyprinid?e, 

 various genera are common to India and Africa, and a close 



Proc. Zool. Soc— 1920, No. XXXVI. 36 



