Geological Society, 3G3 



True .S". CHSciivis occurs in the U[)[)er parts of the Ucayali 

 and Madre de Dios Rivers, considerably further to the north- 

 west than this Bolivian representative of the species. The 

 general colour ot the under surface is on the average markedly 

 more ochraceous in the south-eastern form. 



PKOCEEDIXGS OF LEARNED SOCIETIES. 



GEOLOGICAL SOCIETY. 



August 8th, 1913.— Dr. Aubrey Strahan, F.K.S., President, 

 ill the Chair. 



The following communication was read : — 



'Tlie Miocene Beds of the Yictoria Nyanza and the Geology of 

 the Country between the Lake and the Kisii Higblands.' By 

 Felix Oswald, D.Sc., B.A., F.G.S. ; with Appendices on the Verte- 

 brate Kemains, by Charles William Andrews, D.Sc, F.K.S. ; on 

 the xN"on-:Marine M'dlusca, by llichard Bullen Xewton, F.G.S. ; and 

 on the riant-llemains, by Miss X. Bancroft, B.Sc., F.L.S. 



The Miocene beds of the eastern coast of the Yictoria Xyanza, 

 south-east of Karungu, form a narrow zone (covered with" black 

 earth) at the foot of cliffs of overlying nephcline-basalt, and are 

 only exposed in a few gullies. The whole series is conformable, 

 dipping b^ north by west. 



1. (Beds 1-12.) An upper group (about 70 feet thick) of grey 

 and brown clays and shales, with occasional current-bedded sand- 

 stones containing terrestrial shells {Tropidoi>1wra, Cerastus), as 

 also calcified tree-stems in the uppermost bed. 



2. (Beds 13-25.) A middle group (about 30 feet thick) of red 

 and grey clays, with white sandstones in the lower half, No bone-. 

 bed, but fragmentary Chelonian and Crocodilian remains occur 

 sparsely throughout the series. Persistent horizons are a travcr- 

 tinous marlstone (No. 14) containing AmpuUaria and Lanistea; 

 a thin sandstone (No. 10) yielding Hyracoid jawbones ; and a gravel 

 (No. 24) yielding teeth of Dinolheriim, Protopterus, crocodile, etc. 



3. (Beds 20-37.) A lower group (about 35 feet thick) of current- 

 bedded sandstones and gravels passing down into clays and marl- 

 stones. A conglomerate of calcareous nodules overlies gravelly 

 sandstones (No. 31) containing isolated bones of Dinoiherium, 

 Anthracotheroids, rhinoceros, giant tortoises, etc., indicating a 

 Lower Miocene (Burdigalian) age, with Amjxdlaria, Cleopatra, 

 and terrestrial shells {Cerastus). 



These tluviatile sediments were deposited in a lagoon, and were 

 derived from gneisses, andesites, and quartzites that still occur 

 in xitu to the eastward. Calcareous springs acted intermittently, 

 and the sediments became finer and less fossiliferous as the river- 

 system reached its base-level. 



