Vol. 62.] ROCKS OF WESTERN CAERMARTHEXSHLRE. 605 



(2) Ashy Mudstones, etc. — Passing upwards, the blue-black 

 shales become coarser in texture, and take on the character of ashy 

 mudstones, becoming gritty as they near the base of the grits. 

 They are sparingly fossiliferous, except in some bands in which 

 specimens of Ortliis Carausii, Salt, are fairly numerous. They yield 

 a few dendroid graptolites — the forerunners of the great profusion 

 which was to appear later. Within these beds are several igneous 

 bands, some of which attain a thickness of between 3 and 4 feet. 

 These are best seen in the old quarry on the brow of the hill north- 

 east of Blaenweneirch. They are also seen in an old quarry on 

 the roadside about 100 yards to the west. Here the mudstones 

 have yielded several specimens of dendroid graptolites, but nothing 

 else. This bit of ground has been disturbed by faulting, and the 

 structure is difficult to make out. The ash-bands with their 

 associated striped mudstones are traceable for some distance 

 westward, and surface-evidence suggests that they have been 

 disturbed by two faults before they reach the vicinity of 

 Pantyffynnon Farm, where they are cut off altogether. 



East of the first-mentioned quarry these beds are traceable down 

 the slope with a north-easterly strike due to dip, and are seen in 

 the bed of the stream. They are again observed along the Blaencediw 

 Lane east of the dingle. Here the dips indicate a small anticline, 

 for, where the beds are last seen in place in a small quarry, they dip 

 southward at about 45°. JNear this point they are cut off by an east- 

 and-west fault — probably a thrust. This igneous band has not 

 been seen anywhere else in the district. 



(3) Grits with Ortliis and Trilobites. — The grits, as 

 stated above, are very variable, both in thickness and in texture. 

 They are more or less ashy in some localities, and again at no 

 great distance they assume the character of coarse conglomerates. 

 This variation is accompanied by a rise and fall in the number, as 

 well as by a change in the character, of the fossils. 



These beds, again, are well represented in the neighbourhood of 

 Whitland Abbey, where grits have been extensively quarried. 

 They form the crest of the ridge that separates the valleys of the 

 Oronw and Fenni from near the Abbey to Penyglog. Fossils occur 

 only in certain thin bands, and these are seldom exposed. Trilobite- 

 fragments and a few specimens of Ortliis have been collected near 

 the last-named place, and hear Pantyderi, as well as at several 

 points in the Gronw Valley. 



There is, behind the Abbey mansion, a peculiar tump rising 

 more than 100 feet above the valley-floor. This is made up largely 

 of grits and thick beds of coarse conglomerate, but they are much 

 disturbed by faulting — several fractures being visible in section. 

 The displacement, however, cannot be great. A short distance to 

 the north there are two outcrops, and quarries have been opened 

 in both. The dips here indicate a shallow synclinal fold. Fossils 

 are very rare in these — fossil-bearing bands, presumably, not being 

 exposed at this point. North of Pound-glas in the immediate 



