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Show 1899.] THE MICE OF ST. KJILDA. 85 I suppose, be contended by anybody, so that the question in reality resolves itself into one dealing with the time at which such a connection existed, and whether it has been sufficiently recent to allow of a passage along it of such a presumably recent mammal as a Mouse. Although we cannot expect to decide such questions from a mammalian point of view alone, it is profitable to remember that such " an old land extension connecting Greenland, Spitz-bergen, and Scandinavia with Scotland and Ireland" is relied upon by the Editors of the recently published second edition of the ' Cybele Hibernica' (Introduction, pp. Ii & Iii) as the only reasonable explanation of the presence in Ireland, and undoubtedly native there, of three plants of North-American habitat, two of which are unknown in Continental Europe ; nor would there seem to be any better explanation forthcoming to account for our share in Ireland of certain Invertebrates which are indistinguishable from North-American forms l. Similarly Mr. A. H. Keane2, although writing on a widely different subject, regards the " submarine bank which stretches from Scotland through the Faroes and Iceland to Greenland " as representing " a vanished Continent of great age, which would appear to have still formed dry land in late Tertiary times." But the present paper deals not with the question of a submerged Euro-American Continent, but with the Mice of St. Kilda, and I must content mvself with pointing out in conclusion that the recent exploring expedition to Rockall3, the most westerly rock-islet off the European Continent, found that when trawling at a distance of about 15 miles south of that rock, " the water shoaled to 80 fathoms, and there was brought up in the bag a most unexpected assortment of shallow-water shells, evidently loug since dead. Amongst these were several kinds of Pecten, Venus casino, V. fasci-ata, Mytilus modiolus, &c." In the words of the Rev. W . S. Green, "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 sand-banks, 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 sand-banks had vanished, these mollusks may haAe accommodated themselves 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. 1 See 'Irish Naturalist,' iv. pp. 25, 122; vi. pp. 225, 257. 2 'Ethnology,' 1896, p. 231. 3 See Trans. E. I. Acad. vol. xxxi. pt. 3, pp. 45-46 (1897). |