463 Journ. of the Asiat. Soc. of Bengal. ‘Nov. & Dec., 1915. 
as Caridina nilotica that proved capable of ousting their en 
demic relatives in its lower waters. 
also by introducing from the Ethiopian Region species such 
The aquatic fauna of the Lake of Tiberias must be mainly 
of recent origin. There are a considerable number of species 
endemic either in the lake or in the river-system of which it 
forms a part, but none of these species are in any way highly 
specialized. The only endemic genus is represented by the 
sponge Cortispongilla barroisi, which is only found, so far as we 
know, at one particular spot in the lake. 
Perhaps the most characteristic feature of the fauna of 
deep freshwater lakes in a warm climate that have had a 
is more easily understood.' The evolution of peculiar molluse- 
genera is best shown in Lake Tanganyika, but also in Lake Tali 
“uin Western China and in some of the lakes of Celebes, 
in which remarkable Gastropods with shells of a peculiar 
marine facies are found. In the case of Lake Tanganyika? 
controverted and the Tertiary deposits in the neighbour- 
hood seem to prove definitely that a lacustrine fauna of perfect- 
ly normal type existed in the lake at a period geologically by no 
means remote.’ In the Lake of Tiberias the shells have a 
distinctly marine appearance owing to the fact that they are 
all thick, containing a large amount of calcareous matter, 
and that a few of the commonest species (c.g. Melanopsis costata 
and Theodoxis jordani) are more conspicuously coloured than is 
usually the case in freshwater shells. The latter fact is prob- 
ably no more than a coincidence, while the thickness of 
the shells cannot be due to evolution in situ, but is rather 
! Annandale, Journ. As. Soc Bengal ( IX 71, et : 
2 See Moore’s Volume The Tanga aoe a “ai oped a 1903). 
3 ge recent discussion on this 0 A ie ee G aunt 
paper ** Origin de la Faune fluviatile de | ‘Est Africain”, IX Congres 
Internat. de Zoologie, Monaco, pp. 557-571 (1914), , 
ee 
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