io THE TANGANYIKA PROBLEM. 



ganyika, and in the concluding summaries, attention has 

 been expressly drawn to the fact, that it appears probable 

 that the African ganoids, and certain other portions of the 

 Tanganyika fish-fauna are in reality the now more or less 

 scattered piscine portion of the halolimnic fauna. And in 

 this connection I have emphasised the very remarkable 

 fact that, notwithstanding the opportunities which always 

 exist for fishes to migrate throughout the fresh waters of a 

 continent, actually about half the species of Cichilidse 

 belonging to the Old World are restricted to the confines of 

 Lake Tanganyika even down to the present day. In the 

 succeeding chapters the Tanganyika problem has been 

 considered in the light of all the evidence which is now 

 available. It has been shown in the first place that the 

 halolimnic fauna cannot now be regarded in any other light 

 than as something wholly distinct in origin from the general 

 fresh-water fauna of Africa, and that it is also equally 

 impossible to regard it as anything but the relic of some 

 ancient sea. In conclusion, the possible mode of origin of 

 this marine fauna has been considered together with the 

 value and the significance of the remarkable correspondence 

 which subsists between the shells of the halolimnic gastro- 

 pods and the remains of those found in the deposits of the 

 old Jurassic seas. 



