FAUNA OF THE AFRIl'AN LAKES. 



533 



latter lake 21 peculiar genera occur, as coinpai-ed with 2 in 

 Lake Victoria, 5 in Nyasa, and a single genus in Lake Edward. 

 As concerns Tanganyika, tiie cas3 may be stated even more 

 forcibl}^ by pointing out that 41 genera in all are recognised 

 from the whole continent, of which 21 l)e]ong exclusively to this 

 lake : in other words more than half the genera of Cicblidse 

 known in Africa are confined within the limits of Tangan3dka. 



It may be wortli while to give a few more comparative figures 

 in the case of the three bigger lakes around which interest 

 principally centres. In Nyasa 38 Cichlid fishes are found out 

 of a total fish fauna of 63, which is 60 per cent, of the whcile ; 

 in Yictoria Nyanza 47 out of 86,- which is some 54 per cent. ; in 

 Tanganyika 89 out of 146, or nearly 61 per cent, of the total. 

 With this remarkable total of 89 Cichlid fishes, Tanganyika, in 

 fact, establishes another record, possessing the richest Cichlid 

 fauna in the world. Next note how extremely large a proportion 

 of the endemic species are Cicblidje. In Nyasa there occur 31 

 endemic Cichlid species out of a total of 43 endemic species in 

 the lake, i. e. 72 per cent. ; in Victoria Nyanza 40 out of 60, or 

 66 per cent. ; in Tanganyika 84 out of 121, or 69 per cent. The 

 proportion of endemic genera belonging to this family is even 

 more extraordinary, for all the geiiei-a which are endemic in 

 Nyasa and in Lake Victoria are Cichlidte (the same is true of 

 the single endemic genus found in Edward Nyanza), and in 

 Tanganyika there are 21 out of 26 endemic genera, or 80 per 

 •<3ent. Lastly, the number of endemic Cichlid forms as compared 

 with the total number of Cichlid forms known from the lakes in 

 question is a basis for further striking figures. Thus in Nyasa, 

 out of 38 species of Cichlid^e, 31 are endemic, or 81 per cent. ; in 

 Victoria Nyanza, out of 47 species, 40 are endemic, or 85 per 

 ■cent. ; in Tanganyika, out of 89 species, 84 are endemic, or over 

 94 per cent. 



From a consideration of all these figures it l)ecomes very plain 

 that the large number of unicjue forms characteristic of Tan- 

 ganyika is especially due to a great development of the fishes of 

 this group, and that the same is true, though in lesser degree, for 

 Nyasa and Victoria Nyanza. 



The review of so largely represented a famil}^ must of necessity 

 be brief. The very characteristic genus T'dapia extends to 

 40 species in the list, but though some are peculiar to certain 

 lakes, there are no very striking features of distribution to be 

 noted. The genus Petrochromis appears to be mainly typical 

 of Tanganyika, for though an endemic form occurs in Nyasa and 

 there is a doubtful record from Lake Albert, it is not found in 

 Victoria Ny;:inza or any of the other lakes considered. The case 

 of Ha'plocliromis is interesting as being, on the contrary, a genus 

 wdth a single widely distributed species recorded from Tan- 

 ganyika, while it is better represented in all the other lakes 

 under review. Perhaps a more important — though unexpected — 

 feature is the existence of H. angustifrons and H. graueri in both 



