THE TANGANYIKA PROBLEM. 



CHAPTER XVII. 



GENERAL CONSIDERATION OF THE NATURE OF THE HALOLIMNIC 



FAUNA. 



PAGE 

 On some peculiarities of the fish-fauna in lake Tanganyika — Relation of some of the 

 characteristic forms to both sides of the Atlantic — The character of the fishes 

 of Tanganyika indicate that part of the fish fauna may have originated from a 

 western sea — Peculiarities of the Congo fauna — The Congo depression pro- 

 bably the remains of a former extension of the sea — The age and type of the 

 Halolimnic fauna — Comparison of the hard parts of the Halolimnic animals 

 with fossiliferous remains — The identity between the shells of the Halolimnic 

 gastropods and a corresponding number of forms from the Jurassic seas — 

 Details of this comparison — General consideration of the value of this com- 

 parison — No valid geological objection to it — The number of corresponding 

 points renders it improbable that the correspondence is a coincidence — The 

 Halolimnic fauna would thus appear to be the remains of that of a Jurassic 

 sea — The characters of the other Halolimnic animals in accord with this 

 view — Recapitulation . . . . . . . . . . . 339 



