28 MR. G. A. BOULENGER ON A COLLECTION 
That there are no Halolimnic representatives among the fishes which have hitherto, 
been obtained is no evidence that other fishes of a widely different and possibly of a; 
Halolimnic type may not in future be secured. On the other hand, the fact that the 
Teleostean fishes now existing in Lake Tanganyika should not correspond with the, 
Molluscan section of the Halolimnic group is really what one would expect; for, as I 
have recently shown ', the facies of the Molluscan section of the Halolimnic group is 
almost, if not quite, indistinguishable from that of the Jurassic seas. Except the 
Herring-like Leptolepide, few, if any, ‘Teleostean fishes are represented in Jurassic beds, 
and we should therefore expect the piscine accompaniments of the Halolimnic molluscs 
to be entirely composed of Ganoids and the like. I found a species of Polypterus, 
which I took to be P. dichir, abundant on the southern shores of Lake ‘Tanganyika, 
and it is quite possible that some of the active carnivorous fishes which inhabit the 
open water may be Ganoids too. What the fish is that so much surprised Glaive, 
when he crossed the lake, by attacking the paddles of his boat, is quite unknown, but 
I myself saw these same fishes attack the paddles of my own boat, not 20 miles from 
the spot where Glaive described them, on the west coast of the lake. 
Judging, therefore, from the incomplete character of our knowledge of the fish- 
fauna of Lake ‘Tanganyika, and from the vast antiquity of the lake, as evidenced by 
the Jurassic facies of its molluscan shells, it is only natural to expect that future 
exploration may reveal, among these fishes, forms that are of the highest scientific 
interest from a morphological point of view. I mean that Tanganyika and its 
neighbourhood present one of those few localities where it is legitimate to expect that 
we may discover many forms that in most places have become extinct. 
Our very slight acquaintance with the surface-forms existing in Nyassa and ‘Tan- 
ganyika, and the complete absence of all knowledge of the contents of the deep 
waters of these lakes, unfortunately by no means exhausts the sum of our present 
ignorance of these matters. We have no real knowledge of the extent of the 
Halolimnic fauna, ,beyond the lake in which it was originally discovered. I have 
shown only that this fauna is not present in Nyassa nor in Shirwa, nor yet even in the 
little lake Kela, not more than 20 miles from the Tanganyika shore, and that it 
is extremely probable that it does not extend to Mwero and Lake Bangweolo to 
the west. But for anything that can actually be shown to the contrary, it may be 
present in Lake Rukwa to the east, and in the Albert and Albert Edward Nyanzas 
to the north, and it is perhaps almost to be expected that some representatives 
of this stock should be found in Lake Kivu, which lies in the same great valley not 
more than 50 miles to the north of ‘Tanganyika. But what is the relation of this 
lake, the effluent of which flows south into Tanganyika, to the Albert and Albert 
Edward Nyanzas, with effluents flowing into the Nile, towards the north? All that 
" “On the Hypothesis that Lake Tanganyika represents an old Jurassic Sea,’ Quart. Journ, Microsc, Sci. 
xli, no, 162, June 1898. 
