262 ; . REPORT—1850. 
across the eastern channel, ancient but not anterior to the existing population 
of the British seas, we may ascribe some of the peculiarities of our southern- 
most marine fauna, especially the presence there of southern forms of mol- 
lusks, inhabitants of the Littoral or Laminarian zones, and undoubtedly colonists 
from a more southern assemblage, such as we now see in the Channel Islands, 
The inhabitants of greater depths taken off the Cornish coast at considerable 
distances from shore, we have seen to be species of a different climatal 
character, boreal instead of southern; and when the distribution of animals 
on the Nymph Bank and off the southernmost coast of Ireland shall have been 
more fully explored, we shall find—at least, so the facts already made known 
indicate—that there is a large tract of considerable depth in the southern 
part of St. George’s Channel, of the great deep-sea fishing-grounds, charac- 
terized by this boreal fauna, bearing a close relationship with the extinct 
fauna of the northern drift of the south-eastern districts of Ireland and parts 
of the coast of Wales.. A great part of the Irish sea is very shallow, rarely 
sufficiently deep to affect the character of its fauna; parts of its floor, as be- 
tween the Isle of Man and Lancashire, barely emerging from the Coralline 
zone, and its deepest portions of any extent scarcely infringing on the region 
of deep-sea corals. Between the Isle of Man and the Mull of Galloway, it is 
true, there is the deep and narrow ravine, 150 fathoms in its deepest part, 
discovered by Captain Beechey and dredged by him. But the results of his 
valuable research, carefully investigated by a most able naturalist, Mr, W. 
Thompson of Belfast, have shown that we have no fauna in that limited 
gulf at all corresponding to its depth, and that its contents are normally inha- 
bitants of shallower regions. For this reason, the absence of the assemblage 
of subarctic or boreal. species met with in all the older British submarine 
areas of considerable depth, and the curious interruption in the distribution 
of the smaller terrestrial quadrupeds which occurs in this quarter, reaching, 
as many of them do, the extreme parts of the south of Scotland, yet not in- 
habiting the nearest portions of Ireland opposite or any part of that island, I 
am induced to hazard the conjecture, that the great. ravine in question dates 
its origin from a period later than the close of the glacial epoch, yet before 
that of the general spread of the greater part of the Germanic fauna and flora 
over these islands—of that part which, from causes varying in different spe- 
cies of animals and plants, was the more tardy in its progress. In the regions 
of the Clyde and along the inner Hebrides we have a great variety of depths ; 
but the phenomenon most striking is the great depth of many of the lochs, 
often of considerable dimensions, whilst the entrances to them are exceedingly 
shallow ; and in some cases the seas without them for a considerable distance 
are very shallow also. The fauna of these isolated deeps is very different 
from that of the Gallovegian ravine, for in the former we find assembled and 
imprisoned creatures which are characteristic of very deep regions of the 
sea, and which are mainly of a marked Scandinavian character. Sometimes, — 
as in the neighbourhood of the Croulin islands, between Skye and the Ross- 
shire coast, we find a deep area of the sea thronged with Scandinavian spe- 
cies, living on the remains of the ancient glacial sea-bed and mingled with 
the exuviz of their extinct ancestors, and of other creatures, now wholly ex- 
tinguished within our seas, of an equally boreal or even arctic complexion. 
We have to sail a long way from the islands before we come to the edge of 
the permanently 100-fathom line, which, as we go northwards, must be 
sought for considerably to the west of St. Kilda and north of the desolate 
rocks of Sulisker and Rona. Around the Zetland Isles is the region in which 
the British explorer has the best opportunity of inquiring into the features of 
the fauna of the greater abysses of our seas, though of these depths we can 
scarcely claim more than the 100-fathom region as coming within the com- 
