The Tanganyika Problem Reviewed 469 



140 of which occur in the Amazon; 150 species occur in 

 Africa, 58 of which are found in the Congo area, 10 in 

 Tanganyika, and 41 in the Nile basin. The Characinidae 

 includes 659 species in S. America, of which 317 are found 

 in the Amazon; 98 species are African and of these 52 are 

 from the Congo, 18 from the Nile basin, and 5 from Tan- 

 ganyika. The Cyprinodontidae (Poecilidae) has 160 S. 

 American including 14 Amazon species; 42 are from Africa 

 and 8 of these are from the Nile, i from Tanganyika. The 

 Cichlidae includes 187 species from S. America, 55 of 

 which are in the Amazon basin; 215 species are African, 

 and 85 of these are from the Congo, about 40 from the 

 Nile basin, and 75 from Tanganyika. 



Another important feature, which has been strongly 

 emphasized by Boulenger (joj: 41) and others is, that not 

 merely numerous genera but even species have a distribution 

 that extends across the African continent from Senegal to 

 the Nile. Thus Protopterus, in its three variable varieties 

 or species, extends from Senegal to the White Nile, and oc- 

 curs at 2700 feet elevation in Tanganyika, at 3100 feet in 

 Albert Edward and at 4000 feet in Lake Victoria. 

 Mormynis longirostris has been secured at Stanley Pool 

 on the Congo at 800 feet elevation; at Lake Moero at 

 3000 feet; at Tanganyika at 2700 feet, as well as in the 

 Zambesi. The nearly related M. caschive occurs in the Nile. 



Alarcusenius discorhynchus extends from the Lower 

 Zambesi and Lake Nyasa (elev. 1650 ft.) to Khartum 

 on the Nile (elev. 1252 ft.) ; it has been found at Lofol on 

 the Upper Congo (elev. 3000 ft.), and is closely related 

 to M. tanganicus of Lake Tanganyika (elev. 2700 ft.). 

 Tilapia nilotica is found in Senegambia, on the Niger, also 

 in the Nile river at rather low elevations; it is in Lake 

 Rudolf (elev. 1250 ft.), in Tanganyika (elev. 2700 ft.), in 

 Albert Edward (elev. 3106 ft.), in Victoria (elev. 4000 

 ft.), and in Lake Kivu (elev. 4841 ft.). Similar details 

 might be cited for Hydrocyon lineatus, for Alestes macro- 

 lepidotus, for Paratilapia hloyeti, and other species. 



Now the above is proof that such species once inhabited 

 — more or less densely — an area included within the most 

 distant points where they now exist, and such would cover 



