552 



DR. W. A. CUNNINGTON ON THE 



Name of Species. 



Tangan- 

 yika. 



Victoria 

 Nyanza. 



Nyasa. 



Albert 

 Nyanza. 



Edward 

 Nyanza. 



Otlier parts of 

 the world. 



Unio tangaiiyicensis 



„ teretiusculus 



„ thomsoni 



Buvtonia bouvguignati 



„ taiiganyioensis . 



E 

 E 



Gen. E 

 E 



Gen. E 







P 





R. Nile. 



Family Mutelidj3. 



Mutela alata 



„ bouvguignati .. .. 



., nilotica 



„ subdiapliana 



Pleiodon spekei 



Spatha anceyi 



„ bloyeti 



„ kirki 



„ nvassaensis 



Moncetia anceyi 



P' 

 E 

 E 



Gen. E 



P 



E 

 P" 



iE 



E 



E 



E 

 E 



*P 



P' 



E. Africa. 

 N. Africa. 

 Egypt. 



E. Africa. 



Family Mtu-e^liidm. 



^]theria elliptica 



P 



p 









Tropical Africa. 



5 families 



4 



o 



3 



4 



4 





11 genera 



3E, 5 P. 



(8) 



7 p. 



4 P. 



4 P. 



4 P. 





53 species 



14E,3P. 

 (17) 



12E,6P. 



(18) 



7E,6P. 

 -(13) 



2E,6P. 



(8) 



2E,3P. 

 (5) 





The table of distiibution iu this case displays no outstanding 

 features such as are to be seen in other groups. The not incon- 

 siderable total of 53 species is reached, but the details of 

 distribution have, in most cases, little significance. Firstly, it 

 may be noted that the vast majority of the forms (there are only 

 4 exceptions) are on record merely from a single lake ; secondly, 

 it is interesting to find that no species in the whole list occurs 

 outside the African continent. • 



Victoria Nyanza, as already stated, exhibits the lai'gest number 

 of types, viz. 18, but is closely followed by Tanganyika with 17 

 and by Kyassa with 13. Lakes Albert and Edward follow in the 

 usual order with 8 and 5 species respectively. A fact which 

 emerges from an examination of these figures, is that the two 

 lakes with the highest totals only contain about one-third of the 

 number of species enumerated (Lake Victoria 33 "9 per cent., 

 Tanganyika 32 per cent.). Contrasted with this, the Gasteropoda 

 of Tanganyika constitute over 63 per cent, of the total nimiber 

 of Gasteropods enumerated, while in other groups the corres- 

 ponding figures for Tanganyika reach 80 per cent, and even 

 90 per cent. (Branchiara). 



