xii THE TANGANYIKA PROBLEM. 



CHAPTER VII. 



GENERAL OUTLINE OF THE ZOOLOGY OF THE GREAT 



AFRICAN LAKES. 



PAGE 

 The thirteen Great African Lakes, the fauna of which is more or less completely 

 known — The lakes examined during the two Tanganyika expeditions — Other 

 sources of information — The fauna of Lake Nyassa — Some physical characters 

 of the Nyassa valley — Limitations of the Nyassa fauna — It is that of a great 

 pond — The fauna of Lake Shirwa — Kela— Rukwa — Bangweolo — The fauna of 

 Lake Mwero — The fauna of Lake Kivu — The fauna of the Albert and the 

 Albert Edward Nyanzas — The fauna of the Victoria Nyanza — Nature of the 

 Nyanza depression — The fauna of Lake Rudolf — The fauna of Lake Tan- 

 ganika — Peculiarities of the fish fauna of Lake Tanganyika — The fauna of the 

 great rivers of Central Africa — The distinctive elements of the fauna of Lake 

 Tanganyika — Definition of the Halolimnic group . . . . . .120 



CHAPTER VIII. 



ON SOME CURIOUS FEATURES OF THE DISTRIBUTION OF SPECIES. 



General poorness of the African lake faunas — The faunas of the different lakes are 

 specifically distinct — The faunas of these different lakes do not appear to inter- 

 colonize — The number of species in the Great African Lakes is directly pro- 

 portional to their size — Unique climatic conditions affecting the Great 

 African Lakes — Similarity of lacustrine faunas to island floras — On the causes 

 which tend to the production of species characteristic of the different 

 depressions ............. 144 



CHAPTER IX. 



THE FISHES OF LAKE TANGANYIKA. 

 Descriptions of the eighty-seven species hitherto obtained . . . . .152 



CHAPTER X. 



THE MOLLUSCS OF LAKE TANGANYIKA. 



217 



The normal and Halolimnic gastropods — Details of the structure of the Halo- 

 limnic forms ............ 



CHAPTER XI. 



THE AFFINITIES OF THE HALOLIMNIC GASTROPODS. 



Inter-relationships of the Halolimnic forms — Their primitive characters — They are 

 not comparable to any existing fresh-water forms, but they structurally ante- 

 cede a number of existing marine genera — The Halolimnic gastropods present 

 the appearance of an old marine relic ........ 266 



