Abstract

Dr. S. H. Straw said that this account of the Ludlow succession of the Usk inlier showed it to be a complete succession, without the gaps previously believed to exist.

Though the Ludlow rocks of Usk belonged essentially to the shelf facies characteristic of Shropshire and the Welsh Borderland generally, they showed certain features which linked them with the basin facies of central Wales, especially at their lowest and highest levels. The shaly mudstones of the Lower Forest Beds with their fauna of small brachiopods and very occasional badly preserved graptolites were strongly reminiscent of the Cyrtoceras Mudstones of Builth, though without the slumps, whilst the abundance of Holopella at the top of the succession was also paralleled at Builth. In the middle part of the succession the comparison was with Shropshire rather than with central Wales.

The speaker asked whether the author had any evidence as to the direction from which the conglomerate band in the south of the area had been derived, since at approximately the same horizon in South Wales, south of Llandovery, there were some hundreds of feet of red and purple sandstones and conglomerates, suggesting the existence of a nearby landmass, situated possibly to the south or south-west.

Dr. J. D. Lawson remarked on the contrast in the thickness of the Ludlovian rocks at Usk and at May Hill, where the maximum thickness was 250 feet and the minimum about 12 feet. Deposition was evidently more continuous in the Usk area, but the discovery of