Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/48

26 with red shales to the thickness of 220 feet, resting upon the Spirorbis-limestone, and how in this respect it compares with the sections of Canobie, Ardwick, Patricroft, Alberbury, Warwickshire, Staffordshire, and Nova Scotia.

The section commences therefore at more than the average height above the Spirorbis-limestone at which Permian strata are usually made to begin in English sections.

In group 2, or the lowest usual division of Permian strata, we see how it contains in its breccias, its green, grey, red, and brown sandstones, as well as in its drifted plant-remains, all the varied phases of the group over the wide range embraced by the sections.

In group 3 (middle Permian) this resemblance is also very great. There are the ever present red, white, yellow, and variegated marls; then in the calcareous bands interstratified with those marls, in the rolled and nodular limestones under the Morlas main-coal, in the 25 per cent of carbonate of lime contained in the pyrites of that coal-seam, in the limestone masses of the Coedyrallt rock, as well as in the bedded calcareous concretions of that rock, we have, I think, unmistakably the equivalent of the more massive limestones of the north-east, the "brockrams" of the north-west, the thin limestones of Lancashire, and the calcareous conglomerate of the West Midlands, as well as of the representatives of these in Russia, Saxony, Bohemia, and Nova Scotia.

I now approach that development of coal-measures in the upper part of group 3 of the Ifton section (No. 11) which, to some minds, will form a strong objection to the acceptance of these beds as equivalents of Permian strata. But why? We see how these beds are paralleled by the dark fossiliferous shales of Eden, by the dark shales of Bohemia, and by shales and coal in Nova Scotia. A comparison of the list of fossil plants found at Ifton with that given by Murchison and Harkness, and by Mr. Dawson, in the papers already referred to, and of all these with lists from the continent of Europe, will show a family likeness running through the whole, and will further show how in all those widely distant localities the same new forms appeared in the midst of the survivors of the older Carboniferous flora.

The uppermost sandstones, group 4, by their colour, massiveness, homogeneity, and mineral composition, correspond to the uppermost sandstones of the same group wherever these are developed; while they do not correspond to, or contain within them the representatives of the groups below them. Besides, as I have pointed out, they may be traced at intervals until they are seen lying above the calcareous conglomerate at Alberbury. Their place, therefore, at the summit, and not at the base, of the Permian strata is clearly proved.

The conclusion is therefore to me inevitable, that, in their stratigraphical position, their mechanical arrangement, their fossil remains, and in their mineral composition, the strata of groups 2 and 3 of the Ifton section (No. 11) are the equivalents of the middle and lower divisions of the strata usually described as Permian in this and other countries.