TI1E TANGANYIKA PROBLEM. 
xii 
CHAPTER VII. 
GENERAL OUTLINE OF THE ZOOLOGY OF THE GREAT 
AFRICAN LAKES. 
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. 
The normal and Halolimnic gastropods — Details of the structure of the Ilalo- 
limnic forms . . . . . . . . . . . .217 
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 
