407 
in which the animals live, the foundation is very weak, but it must 
be remembered that the vertical distribution of these species was 
much more incompletely determined when Sars formed his hypothesis 
than it is at present. 
W. Spotswood Green's evidence of a sinking of the sea-bed 
"near Rockall. 
In ,,The Transactions of the Royal Irish Academy", vol. XXXI, 
W. Spotswood Green maintains that the occurrence of numerous 
dead shells of supposed shallow-water molluscs on the Rockall bank might 
support a theory on a former sinking of the sea-bed in that place. 
I quote from his statements the following (1. c. part MI. p. 45 & 
46): when the trawl came up [from a depth of 100 to 80 fathoms] 
we found, m the bag, a most unexpected assortment of shallow- 
water shells, evidently long since dead. Amongst these were several 
kinds of Pecten, Venus casina, V. fasciata, Mytilus modiolus etc. 
How, under present conditions, such shells could be found living 
anywhere on the bank was difficult to understand. It would seem 
to afford the strongest confirmation to the theory that the time is 
not so very long distant when there was more land, with a shallow 
Coast line, and possibly extensive sandbanks where now the pinnacle 
of Rockall is the- only speck acting as a memorial stone to what 
tradition has called the ,,Sunken Land of Buss". After the shallow 
landbank had vanished, these molluscs may have accomodated them- 
selves to a deeper sea than is usual for such organisms to'live in, 
and it may be that it is only now that the conditions are becoming 
too severe for their further existence. There is, of course, the 
possibility that these shells may have come from the bottom of 
icebergs which had grounded in Greenland or Spitzbergen bays, but 
I doubt if in times sufficiently recent such bergs have visited the 
position occupied by Rockall, and therefore the former theory seems 
the more probable. 
The possibility of the shells having been brought as bait for 
the lines of the fishing-boats visiting the bank is, I think, disposed 
4 
