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PRESIDENTIAL ADDRESS. 
ON THE SUPPOSED SIMILARITY BETWEEN THE MOLLUSCA OF 
THE ARCTIC AND ANTARCTIC REGIONS. 
By Enear A. Suita, F.Z.S., ete. 
Read 14th February, 1902. 
Durine the past year, whilst working out the Mollusca obtained by 
the ‘‘Southern Cross” in the Antarctic regions, I had occasion to 
compare the forms from that part of the globe with those from the 
Arctic regions, and I was interested to ascertain how far the supposed 
resemblance between these two assemblages was real or otherwise. 
I should mention that this subject has been more or less fully discussed 
by Professor D’Arcy Thompson, Dr. G. Pfeffer, and others, but not solely 
from the molluscan point of view. I therefore thought that a few 
remarks upon this subject might be of interest to the members of this 
Society. Sir John Murray, in the Transactions of the Royal Society 
of Edinburgh, vol. xxxviii, in his memoir upon the deep and shallow- 
water marine fauna of the Kerguelen region of the great Southern 
Ocean, has referred to this subject at some length, and has given 
a list of identical and closely allied species found in the extra-tropical 
regions of the northern and southern hemispheres and unknown hitherto 
within the tropics. This list includes invertebrates of all orders, but 
the Mollusca, with which alone we are at present concerned, are as 
follows :— 
1. Glomus nitens, Jeff. 
2. Kellia suborbicularis (Mont.). 
3. Mytilus edulis, Linn. 
4. Dentalium keras, Watson. 
5. Homalogyra atomus (Phil.). 
6. Lanthina rotundata, Leach. 
7. Natica (Lunatia) Groenlandica, Beck. 
8. Odostomia Rissoides, Hanley. 
9. Puncturella Noachina (Linn.). 
10. Trochus (Margarita) infundibulum, Watson. 
11. ? Doris tuberculata, Cuvier. 
Since these species have been quoted from the Reports on the 
Gastropoda and Lamellibranchiata of the ‘‘ Challenger’? Expedition by 
the Rey. R. Boog Watson and myself respectively, I have thought it 
advisable to re-examine each of them so as to establish the correctness 
of the identifications, and to make such observations upon the known 
distribution of the various species and genera as may tend to elucidate 
the occurrence of the forms in question in such remote localities. 
