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 facies , 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, Journal of the 
Royal Geographical Society, January, 1901. 
t J. E. S. Moore, “On the Hypothesis that Lake Tanganyika represents an old 
Jurassic Sea.” — Quarterly Journal of Microscopical Science, vol. xli. 
