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CHAPTER X. 



THE FAUNA OF LAKE TANGANYIKA. 



MOLLUSCA. 



The molluscan section of the fauna of Lake Tanganyika 

 consists, as will have been seen from the lists given on 

 page 138, entirely of gastropods and lamellibranchs. Of 

 the latter group little can be said except that the number 

 of distinct specific forms supposed to be related to the 

 genus ttnio is somewhat remarkable. 



The gastropods, on the other hand, form a series which 

 is nowhere even simulated, much less repeated, in any of 

 the other fresh-waters of the world. We find, however, 

 upon consideration of the lists of forms, that a number of the 

 Tanganyika gastropods belong to genera which we might 

 expect to encounter in the fresh-waters of any of the 

 continents. To this normal series belong the following 

 specific types : — 



Limnrea debaizei Bgt. 

 Isidora coulboisi Bgt. 

 Physopsis africana Krauss. 



,, tanganyicre Marts. 

 Planorbis sudanicus Marts. 



Ampullaria bridouxi Bgt. 

 ,, ovata Ol. 



Lanistes jouberti Bgt. 

 Vivipara trilirata Marts. 



Cleopatra guillemei Bgt. 

 Bithynia humerosa Marts. 

 Melania tuberculata Mull. 



,, tanganyicensis E. Sm. 



,, horei E. Sm. 



The nature of the genera containing all the above species 

 is at the present time quite well known to naturalists, 



