LAKE TA-NGANTIKA AN OLD JURASSIC SEA. 303 



On the Hypothesis that Lake Tanganyika 

 represents an Old Jurassic Sea. 



By 

 J. E. S. Moore. 



With Plate 23. 



" For anything that geology or palaeontology can show to 

 the contrary, a Devonian fauna and flora in the British Islands 

 may have been contemporaneous with the Silurian life in 

 North America, and with a Carboniferous fauna in Africa. 

 Geological provinces and zones may have been as clearly 

 marked in the Palseozoic epoch as at present, and those seem- 

 ingly sudden appearances of new genera and species which we 

 ascribe to new creation may be simply due to migration/' 



If the statements contained in this remarkable passage 

 express the truth — and no one acquainted with the forcible 

 arguments which Huxley brought forward ^ in their support 

 will doubt that such is actually the case — it follows as a sort of 

 natural corollary that the existence of our modern fauna and 

 flora may not be incompatible with the co-existence in certain 

 places of extremely ancient types. In several former papers 1 2 

 have laid especial emphasis upon the very singular fact that 

 the fauna of Lake Tanganyika is a double series, that it is in 

 reality composed of two entirely dissimilar faunas which co- 

 exist in the great lake side by side. 



1 Anniversary address to the Geological Society, 1862. 



' ' Nature,' July, 1897, p. 198 ; ' Science Progress,' October, 1897 ; " The 

 Molluscs of the Great African Lakes : — Distribution." ' Quart. Journ. Micr. 

 Sci.,' vol. 41, pp. 159—180. 



