314 Proceedings of Royal Society of Edinburgh. [sess. 
figure largely in Dr Murray’s list. And if we needed (as we prob- 
ably did need) another object-lesson to teach us the danger of 
identifying and classifying species from inadequate material, or from 
inspection of external characters alone, we have lately been taught 
that lesson in a very forcible way by Mr Moore’s research on the 
Molluscs of Lake Tanganyika ; where he has shown that many 
Molluscs which had before been identified by their shells alone, and 
had, on such evidence, been ascribed to lacustrine types, come, in 
the light of anatomical study, to yield the clearest evidence of 
affinities and of sources unsuspected before. 
The facts here brought together also show, chiefly on the 
authority of American naturalists and of the explorers of the Bay 
of Bengal, that in several cases the known range of particular 
species or genera has been of late extended, so that in some groups 
of which before we knew only northern and southern representa- 
tives, we now discern something more of their cosmopolitan 
extension across the depths of the tropical sea. 
I have also sought to show, but very briefly, how, in the cases 
that are left to us, we have apparently to deal with facts for which 
one general explanation will not suffice, but which deserve to be 
examined and if possible explained one by one according to the 
special characters or circumstances of each. 
Lastly, leaving aside the examples chosen by Sir John Murray, I 
have tried to bring together what we know regarding the Antarctic 
fauna in certain groups, especially the Fishes and the Crustacea, 
groups in regard to which our knowledge is of considerable extent, 
and in which specific characters are comparatively plain and unmis- 
takable. In these groups I can find no trace of evidence in support 
of the “bipolar hypothesis.” 
An Examination op Species alleged to be Common to the 
Northern and Southern Extra-tropical Seas. 
Aulocalyx irregularis , F. E. S. — I can find no record of this 
species except those from the Antarctic given in the Chall. Rep., 
Hexactinellida, pp. 174, 176. The types taken off Marion Island, 
46° 4F S., 38° 10' E., consisted of “several much injured and par- 
tially macerated specimens,” of which “ the fragments obtained 
