THE TANGANYIKA PROBLEM. 5 



and the marine gastropods in that lake, cannot be waived in 

 favour of the older geological speculations, which have only 

 negative appearances to support them, and as a matter of 

 fact the newer geological observations are not opposed, as 

 Sir Roderick Murchison insisted, to those oscillations of 

 terra firma which are required in order that such a state of 

 things should have been brought about.* 



Moreover, the impression to which I have alluded above 

 that the marine animals in Tanganyika must be very old, 

 eventually bore further fruit. I remembered having been 

 struck while still on the shores of the lake with the fact that 

 some of the shells there were curiously similar to other shells, 

 either living or extinct, which I had seen elsewhere, and after 

 searching amongst the conchological representatives of the 

 different geological eras, I found that this peculiar character, 

 this distinctive/^^, as the geologists express it, presented 

 by the Tanganyika shells, was again presented by the fossil 

 remains in the beds of the old Jurassic seas, that is in the 

 marine deposits of a little later date than the English coal. 

 The correspondence between the shells now living in Tan- 

 ganyika and these, their long extinct marine Jurassic coun- 

 terparts, is most extraordinarily complete; and perhaps the 

 most remarkable feature about the comparison is that the 

 shell of every one of the numerous marine molluscs of 

 Tanganyika compares in what is practically a specific sense 

 with its individual prototype in the remains of the old 

 Jurassic seas.f 



This being so, it will be seen that the existence of such 

 a correspondence between what I have termed the halolimnic 



* See "Tanganyika and the Countries North of It," J. E. S. Moore, Jotirnal of the 

 Royal Geographical Society, January, 190 1. 



t J. E. S. Moore, "On the Hypothesis that Lake Tanganyika represents an old 

 Jurassic Sea." — Quarterly Journal of Microscopical Science, vol. xli. 



