1906.] OF THE THIRD TANGANYIKA EXPEDITION. 185 



9. Bhazzma. anceyi Boui-guignat. 



ffab, Kibanga. 



One valve only, with five or six radiating ridges down the 

 anterior end. 



c. Post- Pliocene Species. 



Some shells of species still living in Tanganyika were found 

 embedded in a coarse sandy matrix upon the shore at Sumbua, 

 about halfway up the east coast of the lake. One reef was 

 so weathered that the shells {^Neothauma) stood out very con- 

 spicuously, just in the breakers. Three similar reefs occur at 

 intervals inland, on the summits of the former sandy beaches. 

 These shells may be referred to a late Post- Pliocene age. Other 

 specimens occurred in a cliff or ridge, about six feet high, in the 

 north-west part of the Rukwa Valley, where the lake formerly 

 was, but is now dried up. 



So far as one can judge, none of the shells which are more or 

 less perfect, or of those of which there are only fragments, belong 

 to other than recent species, showing that these ridges are of quite 

 modern origin. 



Among those from Sumbua, besides the Neotliatmna, are remains 

 of Rumella^ a thalassoid genus, and of Unio ; and from the Rukwa 

 Valley are fragments of Lanistes, Vivipara, Jlelania, Corhicula, 

 and Unio, all ordinary freshwater types. The araount of material 

 at hand, howevei', is so small, that one cannot say to what extent 

 the thalassoid shells may be represented in the same locality. 



II. Species from the Victoria Nyanza. 



The following species were obtained by Dr. Cunnington at 

 Bukoba on the west shore of the Lake. 



1. Planoebis sudanicus Martens, var. minor Martens. 



Hah. On water- weed in shallow- water inlet north of the town. 



2. Planorbis crawfordi Melville & Ponsonby. 



Hah. Same as that of preceding species. 



Two specimens were obtained, which appear to be inseparable 

 from this species described from Cape Colony. 



3. Melania tuberculata (Mliller). 



Hab. Taken in shrimp-net in a few feet of water in the 

 harbour. 



4. Vivipara constricta Martens. 



Hah. Dredged in about a fathom in the harbour. 



The specimens of this very variable species from this locality 

 are rather like Martens's figure (' Beschalte Weichthiere Deutsch- 

 Ost-Afrika,' vol. iv. pi. vi. fig. 20), but they exhibit a third keel 

 between the two represented in the illustration. They are more 



