of an Arctic flora as we find on the Scottish mountains was aided, perhaps mainly
hy land to the north now submerged. I t is difficult otherwise, too, to account for
the cessation of the Arctic littoral Mollusks in the Scottish glacial beds, and their
replacement by other forms on the English and Irish beds of the same epoch.
When dredging on the great fishing-banks bounding the Zetland Isles and forming
long ridges now 50 and more fathoms below the sea, stretching from some
unexplored point in the north, like long arms, down to the Scottish shores, and
covered m th angular fragments of the rocks of which they are formed, I was
strongly struck with their resemblance to the rugged and broken surfaces of the
neighboiu'ing islands, and could not divest myself of the notion that these banks
were submerged mountain-chains. Before, however, this can be fairly assumed,
we must have a re-examination of the vegetable and animal productions of
Iceland, that great centre of volcanic power, the presence of which where it is,
is possibly connected intimately with the phenomena we have been endeavouring
to interpret ” *.
The outline thus shadowed forth of that ancient barrier which is supposed to
have stretched across from East Greenland (probably, however, at some point far
to the northward) towards the shores of Northern Europe derives a singulai-
degree of confirmation from the soundings. For, on reference to the map, it will
be seen that a vast area of sea-bed to the southward of Iceland, extending to the
30th degree of west longitude on the one hand, and to the Faroe Islands and
Hebrides on the other, gradually diminishes in depth as it advances northwards,
in all probability constituting the boundary of an archipelago rather than a continuous
continent, across which the various species of animals and plants made
their way southwards. AVhen that archipelago existed, the Hebrides and Faroe
Islands were probably united, whilst Eockall formed a large but distinct island,
and another still larger island rose up out of the sea between the 57th and 60th
degrees of latitude, and about the 30th degree of west longitude. On the northern
flank of this island the Star-fish sounding was taken. Lastly, the Faroes and
Iceland were then separated only by a narrow channel, situated about the I5th
* ‘ Memoirs of the Geological Survey of Great Britain,’ vol. i. p. 398.
I cannot refrain from here paying my humble tribute of admiration and respect to a lamented friend
and coUege-mate. The first time I ever saw a dredge put down was in the Firth of Forth, in company
with Edward Forbes, nine and twenty years ago.
degree of longitude, whilst the AVestmann Islands and the Blinde Skier respectively
formed portions of the southern and south-western coast-line of Iceland.
Viewed by itself, the subsidence of this large tract, although of interest as yielding
a glimpse of the facies of the ancient Atlantic, and even suggestive of the
acclimatization of the creatures now distributed over its bed, could hardly have
been regarded in a higher light than as offering a plausible explanation of a
most unlooked-for phenomenon. But it assumes a far more important bearing
when coupled with the fact that these creatures belong to existing shallow-water
species, and that they exhibit no appreciable trace of variation, notwithstanding
the change of conditions to which they have been subject for a vast series of
generations. In short, no proof of subsidence could be more complete, no proof
of the truth of the doctrine of single specific centres more convincing, than the
detection under such circumstances of a colony of acclimatized Star-fishes,
belonging to a species typical of the Boreal province, weU known to range from
the confines of the arctic circle to our own shores, and already shown to have
accommodated themselves to a depth of 200 fathoms without variation; whilst
the fact of subsidence being general throughout the whole area is rendered
probable by the discovery of sessile Annelids, also belonging to known shallow-
water species, at a depth of 680 fathoms, halfway between Iceland and the
Faroe Islands.
The occurrence of a shallow-water Serpula at such a depth is important, moreover,
from the evidence it yields of the subsidence having been extremely gradual,
and not merely the result of local and temporary submarine volcanic action; for,
whilst creatures having powers of locomotion might have evaded the consequences
of sudden subsidence by migration to shallow water, the sessile Annelids must
inevitably have been destroyed. I f these facts are correct, the detection of
shallow-water species on isolated submerged areas of sea-bed may yet enable
us to determine whether such areas have been nearer the surface at some anterior
period, and may thus afford us a glance, otherwise unattainable, at the lost landmarks
of a bygone geological epoch.
I t will perhaps be asked how it is that the OpldocomcB, if descendants of a
littoral species, exhibit no definite divergence of character from individuals of
the same species which have never been removed from normal conditions. To
this it may be answered that certain orders of animals are known to be much