ON BRITISH MARINE ZOOLOGY. 263 
pass of British natural history. The soundings for a degree and a half north 
of Unst do not reach 300 fathoms; and from the Naze of Norway to the 
coast of Scotland there is a line of soundings not reaching to 100 fathoms, 
quite sufficient, as may be seen from an examination of the tables here 
given, to keep up a considerable communication and interchange with the 
Scandinavian marine fauna. 
That the diffusion of Lusitanian forms along our southern shores and for 
some distance up St. George’s Channel is due to the action of southern cur- 
rents and their climatal influence, must be evident to any person who will 
compare the range of those species with the course and extension of Rennell’s 
current, which, striking towards our shores from the coast of Spain, im- 
pinges on our south-western English provinces and diffuses its influence over 
an area exactly corresponding with the extension of our marine creatures of 
southern types. The extension, more or less powerful in different years, of 
the Gulf-stream towards the Irish coast, and the combined influence of it 
and its branch-current already mentioned, affects an area extending from our 
south-western English province round the western coast of Ireland and im- 
pinging on the western shores of Scotland in its northern portion, sufficient 
to account for the curious curve.of distribution taken by those animals 
which range in that line almost from Devon to Zetland, but are rare or 
absent in the central portions of the Irish sea. The setting-in of the arctic 
current from the centre will account for the transmission to our northern 
shores of numerous Scandinavian forms. But no action of currents, as at 
present maintained, can account for the isolated patches and imprisoned 
assemblages of glacial animals to which I have more than once alluded in 
this Report. To account for them we must trace the physical conformation 
of the British seas in an epoch anterior to the present, and by doing so, shall 
find that the causes similar to those now in action differently disposed, will 
give us a clear insight into the origin of these phenomena. I have elsewhere 
theorized fully on this subject*, and have only to add, that all subsequent 
researches, a great mass of which is embodied in this Report, go in the 
strongest manner to confirm the views I had ventured to advance. 
Desiderata within this area.—A great deal may yet be done for the ex- 
ploration of the part of the British seas which has furnished the subject of this 
Report. Although little that is new, if anything, can be expected from the 
coasts of Hants, Sussex and Kent, yet it would be satisfactory to have a 
well-filled series of dredging papers relating to those counties. The central 
portion of the English channel and its entrance have yet to be systematically 
explored, and the depths of the Cornish coast and around the Seilly Isles 
should be sedulously examined. Off the entrance of the Bristol channel are 
isolated, or nearly so, patches of 60 fathoms and thereabouts which require 
to be carefully explored. The deeper portions of the Irish sea should be 
looked to more minutely. A more difficult task, and one which can be 
hardly hoped for fulfilment without the help of a steam-vessel and continued 
calm weather, is the dredging of the deeps off the Hebrides in the open 
ocean. Much of the deep sea area around the Zetlands is sure to reward the 
explorer. The lochs of Sutherlandshire have not as yet been systematically 
examined. And lastly, though I fear the consummation, however devoutly 
wished for, is not likely soon to be effected, a series of dredgings between 
the Zetland and the Faroe Isles, where the greatest depth is under 700 fathoms, 
would throw more light on the natural history of the North Atlantic and on 
marine zoology generally, than any investigation that has yet been under- 
taken. 
* Memoirs of Geological Survey, vol. i. 
