422 REPORT—1890. 
There should be some way of accounting for the disparity of these 
exotic faunas ondifferent sides of a not over wide sea, and the sug- 
gestion I would offer is this. Noticing that the unknown or extinct 
element is so palpable in Wexford, and that the quasi-Mediterranean or 
southern influence passes by way of Ballybrack into the Isle of Man, it 
is evident that if a fauna of similar facies can be found to the south, it is 
there that we should look for the origin of such faunas as occur in the 
south-east of Ireland and elsewhere as above referred to. Such a fauna 
as I have already pointed out occurs at St. Erth in Cornwall, but of a 
much earlier date. This will account for their extinct and southern 
forms, but not for the large number of northern species, species to be 
noted, all of Norwegian and Scandinavian types, and not high Arctic, 
none of which are present at St. Hrth. If any hydrographical map of 
the area of the Irish Sea is consulted, it will be seen that the greatest de- 
pression exists in a line not more than a mile broad, running nearer 
the Irish coast than the English, the 30-fathom line passing outside the 
Isle of Man from the Mull of Galloway to St. David’s Head, South Wales. 
Continuing northwards there are two routes available, one opening vid 
the Sound of Jura, and the line of the Caledonian Canal into the Northern 
Sea at the Moray Firth, the other by way of the Clyde to the Firth of 
Forth. Both routes were probably available. The neighbourhood about 
Fortwilliam, at the entrance of the Canal, is fossiliferous, and when 
worked as carefully as other Scottish beds have been, should show good 
results. On the other hand, from the west to the east of Scotland by 
the Clyde-Forth route and north to Banff, the early glacial clays are 
replete with species of the same northern or boreal type as occur in ire- 
land, and in one or other of these directions must the fauna have travelled 
before the line of depression was fully developed, otherwise it is difficult 
to imagine either the northern fauna passing southwards or the extinct 
forms northwards into the Isle of Man within the 30-fathom limit, crossing 
a depression varying from 93 fathoms off Dublin to 194 off Belfast 
Lough. 
Taking Ballybrack as the next in order, the fauna exhibits southern 
influences in its Woodia, Pecten, and Mediterranean forms, and is in the 
opinion of the writer equal in time to the Selsey bed in Sussex, equally 
southern in its origin and unmodified by northern influences by its posi- 
tion being barred by land from northern or western waters. 
The final deepening and opening of the channel round the south of 
Ireland culminated in the final separation of Ireland from the mainland, 
and permitted the introduction of West Indian species of Bulla and Oliva 
jaspidea vid ? the Severn straits, into the Worcester gravels. Going north 
in the same direction into Cheshire and Lancashire southern influences 
are still felt in the lower levels, but there is no evidence whatever of the 
existence in N.-W. Wales, Cheshire, or Lancashire of any marine deposits 
corresponding to the glacial clays of N.-E. Ireland, or the Scottish clays 
of Bute, and the shelly gravels at elevations of 800 feet and upwards 
probably correspond to those at 800 feet to 1,200 feet in the Dublin and 
Wicklow mountains. If these conclusions are correct the present Irish 
Sea must have been represented by a comparatively narrow belt of water, 
and Wales formed a large island separated on its eastern side from 
England by the line of the Severn Sea, anterior to the deep submersion 
necessary to carry the shells to such heights, the re-elevation of the land 
leaving the Irish Sea in its present area. ; 
