﻿Vol. 66.] GEOLOGY OF THE DISTRICT AROUXD LLANSAWEL. 413 



strike up the steep hill on the west to Pant-glas, flaky, thinly-bedded, 

 nncleaved, orange-stained shales occur. No fossils were found, but 

 lithologically the rock is identical with that seen near Cwm Dawe. 

 A little farther along the western road above Pant-glas, grits 

 become more numerous, and are interbedded with thin layers of 

 black shales. Cleavage has once more appeared, and the shales 

 are shivered up between the grit bands, giving a very characteristic 

 appearance. 



(ft) Section on the Gorlech. — (C x ) Half a mile above 

 Abergorlech the ridge of the Clynmarch Grits crosses the stream, 

 making a sharp feature, and the rock has been quarried high up on 

 the eastern slope, in the wood. The lithological characters are 

 identical with those seen in the quarries of Clynmarch and Sunny- 

 bank, and the following fossils were obtained : — Monograptus 

 cyphus, M. cf. atavus, 0. T. Jones, Olimacograptus rectangular is, 

 01. hughesi, Nich., and Orthograptus mutabilis (?). 



(c) (C x ). — Nearly 2\ miles from Clynmarch, along the ridge to 

 the north-east, the cyphus grits and shales are exposed again in a 

 quarry in a wood, east of Cefn-telych. The beds dip 50° north- 

 westwards, exhibit the characteristic lithology, and yield the typical 

 fossils. 



(C 3 ). — Two- thirds of a mile away to the north, high on the side 

 •of a hill, is a small quarry opened up in shales and thinly-bedded 

 grits, the former uncleaved, smooth, and splitting up into thin 

 laminae. These beds (L. 16 on the map, PI. XXIX) yielded grapto- 

 lites in a verj T bad state of preservation ; they have doubtfully been 

 referred to Monograptus marri, M. runcinatus, and M. galaensis (?). 

 "We therefore associate the beds with the Pengrelli Shales. 



Y. Detailed Structure of the Outcrops of Conglomerate. 



The complicated structure of this district is only brought out by 

 detailed mapping. At the east of the Shon Nicholas ridge, where 

 it is crossed by a mountain road, the conglomerate is exposed for 

 75 yards across the strike. A short distance to the south-west 

 along the strike, a small subsidiary roll brings up the conglomerate 

 again to the north-west of the main ridge. This small dome dies 

 out in about 600 yards, beyond which the main outcrop widens, 

 attaining its maximum width of 220 yards, three-quarters of a mile 

 from the road mentioned above : at this point the direction of the dip 

 is north 30° west. The base of the conglomerate is clearly marked by 

 a well-defined feature, and at the western end of the hill is seen 

 to swing round in accordance with the change of strike which sets 

 in. The dips change first to north, then to south 60° east ; while 

 a north-westerly dip between them indicates a small secondary 

 roll. The conglomerate outcrop also diminishes steadily in width 

 and, after striking north-eastwards for a distance of 220 yards, ends 



