Vol. 70.] MOLLTJSCAX REMAINS FROM THE VICTORIA NTASTBA. 187 



Appendix III. 



On some Xox-Marixe Mollpscax Remains from the Victoria 

 Nyaxza Reciox, associated with Miocene Vertebrates. 1 

 By Richard Bullex Newtow, F.G.S. 



[Plate XXX.] 



Introduction. 



The material on which this communication is based was 

 •obtained by Dr. Felix Oswald from a series of fluvio-lacustrine 

 deposits occurring at Nira, Kachuku, and Kikongo, which are 

 situated east of Karungu Bay, and therefore near the north- 

 eastern corner of the Victoria Xyanza, the furthest-removed locality 

 from the lake-margin being Kikongo, which is distant some 5 or 

 •6 miles. 



From geological observations made at these places, Dr. Oswald 

 was able to construct a vertical section showing that the rock-suc- 

 cession was divisible into thirty-seven beds of variable thicknesses, 

 which, when added together, amounted to a total thickness of about 

 160 feet. Speaking generally, the mollusca were found through- 

 out the deposits, and often in association with a small species of 

 Dinotherium, and Chelonian, Crocodilian, and other vertebrate 

 remains. The most valuable of these fossils was the Dinotherium, 

 because it unmistakably indicated that the deposits containing it 

 might be referred to the Burdigalian stage of the Miocene Period. 

 Stratigraphically, then, this was an important result ; but it had 

 been arrived at previously to the ' Oswald ' expedition by Dr. C. W. 

 Andrews, F.R.S., 2 who reported on similar Dinotherium remains 

 from the same area, which had been collected by the late Mr. D. B. 

 Pigott, and were afterwards presented to the British Museum 

 by Mr. C. W. Hobley, C.M.Gr., one of the Commissioners for 

 British East Africa. From a fragmentary mandible with teeth 

 in situ, Dr. Andrews was enabled to recognize a new species of 

 this genus, figuring and describing it as D. hobleyi, as well as 

 pointing out its affinities and ranking it as ' closely similar to 

 D. cuvieri ' of Kaup, a characteristic mammal of the Burdigalian 

 beds of France. 



It is fortunate, therefore, that the vertebrate evidence enables us 

 to determine so accurately the horizon of the deposits, because the 

 molluscan remains would have utterly failed in this direction, from 

 the fact that the} 7 represent existing species. The collection consists 

 entirely of gastropod genera of fluviatile and terrestrial character 

 belonging to Ampullaria, Lanistes, . Cleopatra, Tropidophora, 

 Achatina, JBurtoa, Cerastus, and Limicolaria — the total aDsence 

 of Pelecypoda being incidentally mentioned as remarkable, since 



1 Communicated by permission of the Trustees of the British Museum. 



2 ; On a New Species of Dinotherium (D. hobleyi) from British East Africa' 

 Proc. Zool. Soc. London, 1911, p. 943 & pi. xlviii. 



