THE TANGANYIKA PROBLEM. 335 



was, at any rate once, wide-spread in Africa ; and that a 

 large percentage at least of the halolimnic shells correspond 

 to those in the upper cretaceous fresh-water beds. 



Dr. Gregory was consequently of opinion, before the 

 second Tanganyika expedition started, that we should 

 encounter the halolimnic fauna in other African lakes ; 

 or at least in the old lake deposits which occur in asso- 

 ciation with them, outside the region of Tanganyika 

 altogether. This view, however, has entirely broken 

 down, as it is now known we did not encounter the halo- 

 limnic fauna outside Tanganyika. It is not present in 

 Nyassa, Shirwa, or even Kivu ; it does not occur in Bang- 

 weolo or Mwero. It is not present in the Albert Edward, 

 the Albert or the Victoria Nyanzas. It does not occur 

 in Beringo, nor yet in Rudolf. Neither did we find the 

 remains of the halolimnic forms in any of the numerous 

 old lake deposits which we examined or heard of, through- 

 out these regions. 



There is thus, at the present time, not only evidence to 

 show that the fresh-water fauna of the type of that occurring 

 in the upper cretaceous beds is not now characteristic of the 

 great African lakes, but, also, much to show that it never 

 has been so at any time. Further, the comparison between 

 the halolimnic shells and those of the Southern European 

 and American fresh-water cretaceous beds rests, as I have, 

 said, upon the flimsiest ground. Solely, as a matter of fact, 

 on the supposed identity between shells of the Parame- 

 lania of Tanganyika and the Pyrgulifera of these creta- 

 ceous beds. 



I carefully examined all the figures of these shells, and all 

 the fossil specimens contained in the collections of the 

 British Museum from these districts. But, beyond the 

 Pyrgulifera, could find no other shells among the cretaceous 



