282 Ilejwrts and Proceedings — Geological Society of London. 



occurring a little way above the Low Main coal-seam. The entire 

 junction, so far as it can be seen at the base of the cliffs and on 

 the foreshore, many parts of which are only swept clear during 

 exceptional weather, has been studied as opportunity oifered during 

 a series of years. The unconformity is shown by discordance in dip, 

 by overlap of the Table Rocks Sandstone, and by the existence of 

 a pebble-bed, containing fragments of the mussel band and other 

 parts of the underlying series, in the lower part of this sandstone. 

 But the upper, more massive, beds in the section have been thrust 

 in a northerly direction over the lower and more yielding beds, the 

 plane of gliding corresponding accurately along parts of the section 

 with the plane of erosion. Towards the north of the section the 

 beds of the upper series are weakened by intercalated bands of shale, 

 and then differential action has been set up. The result is that the 

 thrust-plane is no longer a simple one coinciding with the uncon- 

 formity, but extends some way above it. The effects of the thrust 

 are seen in the ploughing up, folding, and faulting of the lower 

 series, in the penetration of tongues of sandstone from the upper 

 series into the lower, in the curling up and shattering of the pebble- 

 bed, in the puckering and hardening of the shale, and in the 

 blending of fragments of various rocks subjected to its influence. 

 The marks of intense action are practically confined to the surface 

 of the beds of the lower series. The action of the thrust is 

 markedly rhythmical, and its effect is to mask the unconformity ; 

 and the great discordance in dip which is at times produced is 

 no criterion of the unconformity. Although the amount of rock 

 removed by intro-Carboniferons denudation from the lower series 

 is unknown, chemical and other evidence is given to show that 

 the lower series has undergone weathering and some leaching out 

 of constituents in the interval between the two series. 



2. " The Carboniferous Succession below the Coal-measures in 

 North Shi'opshire, Denbighshire, and Flintshire." By Wheelton 

 Hind, M.D., B.S., F.R.C.S., F.G.S., and John T. Stobbs, F.G.S. 



This paper opens with a critical account of previous research 

 among the Carboniferous rocks of North Wales, chiefly the work of 

 the late G. H. Morton, Mr. R. Kidston, and Mr. A. Strahan. There 

 follows a detailed account of the various beds, exposed in numei'ous 

 quarries worked for road-metal, iron manufacture, lime, cement, 

 chert, or building stone. Fossil lists are given from each exposure 

 of importance. The lower series of the Carboniferous Limestone, 

 as developed in the Bristol area, was never deposited in this district, 

 where the lowest beds contain fossils characteristic of a comparatively 

 late phase of the Carboniferous Limestone Period. Whether this 

 was due to irregular configuration of the ocean floor of that age, 

 or to contemporaneous earth movement of a regional character, 

 cannot as yet be determined. The base of the limestone is 

 characterized by Daviesiella (Prodactns) UangoUensis, and appears 

 to correspond with the junction of the Upper Seminula and Lower 

 Dihuno2)hylhim Beds of the Bristol area. The next limestones in 



