Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/360

Rh of which are seen more especially in Cornwall and Deron, and in the south-east of Ireland. This flora—a relic of a larger—is undoubtedly a part of that which we find in the Channel Isles, and in the adjacent provinces of France. It is still more southern in character than No. III., exhibiting the features of the transition between the great flora of central Europe and that of the southern or Mediterranean region.

When we look to the geological features of the districts occupied by this Devon or Norman flora, we see that its course is marked by the remains of a great barrier, the destruction of which probably took place anterior to that of the formation of the higher and narrower parts of the Channel. It marks, too, the course of the southern bound of the glacial sea.

But whilst I incline to the view that the Kentish and Devon floras are anterior in migratory origin to the Glacial and Germanic, yet I do not press it as essential. For since the Straits of Dover could not have been opened out until the destruction of the greater and all the central part of the Germanic plain, it might fairly be held by those who may object to the survival of the two floras in question, when bounding the glacial sea, that their migration was coeval with the Germanic migration; that the English Channel is of post-pliocene origin, and that the great Devonian barrier was not destroyed until the close of the Glacial period. The holders of such a view would, of course, reduce the epochs of migration to three, instead of five. Such a view would not in the least aflect the general truth of my theory.

Whatever doubts may be entertained respecting the antiquity of the Kentish and Devon floras, there can be none (if my premises be granted) respecting that which I have numbered I., and from which the peculiar botanical character of the south-west and west of Ireland is derived. The number of species included in it does not reach a score, but most of them play an important part in the mountain vegetation of the region. The remarkable point concerning these plants (for as yet no terrestrial animals of this period have been noticed, nor from what I shall presently have to say is it likely there are any now existing) is that they are all species which at present are forms either peculiar to or abundant in the great peninsula of Spain and Portugal, and especially in Asturias. No existing distribution of marine currents will account for their presence, and even if there were plausible grounds for attributing it to the great current known as Rennel's which sweeps the northern coasts of Spain, and strikes in its after-course against the western shores of Britain and Ireland, the plants in question, instead of being where they are, should be present in the southern districts of the countries bounding the English Channel,—in the region of the Devonian flora, where they are not. Nor can we suppose that