appear to the north of Londonderry and then have dark hard rocks that are more or less metamorphous. The former are evidently of Carboniferous age laid down after the formation of the Creguists while the metamorphic sedimentaries are of earlier Paleozoic age. I should rather think they are of pre Siluric age, they extend at least to the southern end of the lake on the divide near Ballymote, a few miles further north the granitic core is at hand. Immediately on the north side of the Creguists we see the deep red shales of the Windsor series, and I also thought that some of these shales farther south in the mountains have had been metamorphosed by the igneous intrusions of the mountain core. In this case the Windsor strata extended across the Creguists area either because they were then not in existence or had been folded to a penplan. I should rather think that the Creguists came into existence at the close of the