1851.] OF THE ROYAL INSTITUTION. 19 
presence of peculiar forms which gives them a distinctive character. 
All recent researches, when scientifically conducted, have confirmed 
this classification of provinces of depth. When we have an appa- 
rent exception, as in the case of the submarine ravine off the Mull 
of Galloway, dredged by Captain Beechey and recorded by Mr. 
Thompson, in which though it is 150 fathoms deep, the fauna 
is that of the coralline zone, we must seek for an explanation of 
the anomaly by enquiring into the geological history of the area in 
question. Inthis particular instance there is every reason to believe 
that the ravine mentioned is of a very late date compared with the 
epoch of diffusion of the British Fauna. 
When we trace the horizontal distribution of creatures in the 
British seas, we find that though our area must be mainly or 
almost entirely referred to one of the great European marine 
provinces, that to which the Lecturer has given the name of Crtric, 
yet there are subdivisions within itself marked out by the presence 
or absence of peculiar species. The marine fauna and flora of the 
Channel Isles present certain differences, not numerous but not the 
less important, from that of the south-western shores of England, 
which in its turn differs from that of the Irish sea, and it again from 
that of the Hebrides. The Cornish and Devon sea fauna and that 
of the Hebrides are marked by redundancies of species; that of the 
Eastern coasts of England on the contrary by deficiencies. Along 
the whole of our western coasts, whether of Great Britain or Ireland, 
we find certain creatures prevailing, not present on our eastern 
shores. In the depths off the scuth coast of Ireland we find an 
assemblage of creatures which do not strictly belong to that pro- 
vince, but are identical with similar isolated assemblages on the 
west coast of Scotland. In the west of Ireland we find a district of 
shore distinguished from all other parts of our coast by the presence 
of a peculiar sea-urchin to find the continuation of whose range we 
must cross the Atlantic to Spain. In such phenomena the Lecturer 
sees evidences of conformations of land, of outlines of coast and 
connections of land with land under different climatal conditions 
than at present prevail within our area, for an explanation of which we 
must go back into the history of the geological past. If we do 
s0, we can discover reasons for these anomalies, but not otherwise. 
The dredging researches about to be published go to show that 
among our sublittoral animals the northern element prevails over 
the southern,— a fact indicated by the number of peculiar northern 
species; at the same time the southern forms appear to be dif- 
fusing themselves northwards more rapidly than the northern do 
southwards. This diffusion is mainly maintained along our western 
shores, and appears to be in action, not only in the British seas, but 
also along the shores of Norway. We must attribute it to the 
influence of warm currents flowing northwards, originating probably 
in extentions of the gulf-stream. The body of colder water in the 
depths of our seas preserves the original mhabitants of this area, 
C 2 
