﻿154 MR. W. G. FEARNSIDES ON THE [May I9IO, 



Thickness in feet. 

 130 



Black rock with blue streak. Outside surfaces covered with 

 thick rust 6 



Intensely black rock with black streak. Very finely laminated. 

 Shining mica-flakes along the bedding. Bedded in 4- to 5-inch 

 bands. Veryrusty 6 



Blocky black rock, showing black outside, finely laminated 

 within, and having visible colour-bands, up to a quarter of an 

 inch thick, at intervals of about 3 to 4 inches. Some of the 

 beds are nodular 12 



Hard black calcareous nodules alternating with splintery black 

 shales. The topmost band appears almost pisolitic, the lowest 

 is like an ashy grit, but weathers to a rottenstone. Mica- 

 flakes abundant, lamination well marked 6 



Black non-laminated slates, with band of cone-in-cone ironstone 

 concretions weathering out into holes, measuring 3 by 2 by 

 I foot at the base 6 



Banded blue-black and dark-grey slates, soft, and rusting deeply 

 with a thick crust. Cleavage rather good ; bad fossils occa- 

 sionally, Parabolina spinulosa 8 



Rock not exposed. Once eaten out into a cave 6 



Dark-grey, finely-banded splintery flags,, smooth, and grey- 

 weathering on the outside. Parabolina spinulosa not rare ... 10 



Dark-weathering splintery flags, breaking into fragments which 

 measure often about 12 inches by f by \ inch. These during 

 weathering become covered with a hard dark crust, and where 

 broken in the cliff have often had their cores removed, leaving 

 holes like finger-stalls 6 



Grey dark-weathering flags, with ill-defined knobby ringers ... 10 



Bright-weathering grey flags, banded in the upper part, and 

 with a prominent 1-foot ringer at the base. Crowded with 

 Lingulella davisii 20 



Total 226 



The road and stream-section south of St. Beuno's Church at 

 Penmorfa does not lend itself to absolute measurement, but the 

 total thickness exposed is much the same as at Ogof-ddu, and the 

 variations of lithology follow the same order. The Parabolina Beds 

 at the base have their trilobites unspoiled by cleavage, and the 

 overlying impure limestone-hands, seen under the southern wall 

 of the road where it rises from the corner towards Coed Bryntwr, 

 are rich in Orthis lenticular is, the remains of which probably supply 

 the calcareous material. The very black beds above these contain 

 Agnostus pisiformis sparsely throughout, and also yield occasionally 

 the compact tails of a Niobe-like trilobite. The SphcerophtJialmus 

 Beds crop out in the ditches on either side of the road from Tyn-llan 

 Farm down to Wern, and the Peltura Beds lower down the same 

 road and south of the burn. 



The Wern gate-cutting exposure, the field-side cuttings, and the 

 blocks of slate ploughed up in the arable ground above Llanerch, 

 and between Llyn Gareg-wen and Borth, have long been known 

 as hunting-grounds for those who would collect trilobites from 

 the Black Band. At each and all of these localities the detailed 

 succession confirms the section measured at Ogof-ddu, and goes to 



