﻿Vol. 66.] GEOLOGY OF THE DISTRICT AROUND LLANSAWEL. 409 



in every direction with massive quartz-veins containing a large 

 quantity of pyrite. The country rock is, when fresh, a tough blue 

 mudstone, very similar to that in the Llathige quarry, but when 

 weathered it splits into thin rusty splinters. From these cuttings 

 no fossils were obtained. 



A quarter of a mile to the south-west, at Ogof-y-Cawgiau, the 

 rock is not so massive. Thin gritty bands are seen, and fossils are 

 frequent (L. 5 on the map, PI. XXIX). Dips of 15° north-west- 

 wards were noted, and the following fossils obtained : — Mesograptus 

 modestus (small form), Climacograptus medius, and CI. rectangularis. 

 Some 300 yards to the south-west (L. 4) a shaly bed in the mud- 

 stones has furnished Climacograptus tbrnquisti, CI. rectangularis (?), 

 and Glyptograptus persculptus. 



Half a mile south-south-west of Llansawel a tough, well-banded, 

 grey and black shale is clearly exposed in a field-track (L. 3). The 

 rock is seen dipping at an angle of 34° north, 25° west, and yielded 

 Mesograptus modestus, Climacograptus normalis, and CI. medius. 



Just over a mile from Llansawel, along the Abergorlech road, a 

 track leads off to Tre-glog and Acheth, and here a considerable 

 amount of rock is exposed ; but, unfortunately, fossils were only 

 found at one point, and these were in a very bad state of preser- 

 vation. Around Tre-glog, and in the track to Acheth-uchaf, the 

 rock is a highly-cleaved soft and slightly nodular shale, with a very 

 yellow or sometimes metallic weathering ; and the fossils were 

 obtained from a sandier bed, three quarters of an inch thick, by a 

 gate a quarter of a mile from Tre-glog (L. 2). The only form 

 identified was Climacograptus normalis, Lapw. Beyond this bed 

 the rock changes, and hard, blue-grey, banded mudstones are seen. 

 Cleavage is still intense, and the weathering is a rusty brown. 

 This is the nearest point to the cyplius grits where we have 

 obtained exposures, and thus it was particularly desirable to find 

 fossils. But we were entirely unable to do so, and the rock looked 

 so unpromising that we believe it to be barren. From its position 

 it should be in the neighbourhood of the zone of Monograptus atavus 

 and M. rheidolensis, and the description of these beds in the Pont 

 Erwyd district, with the change from soft shales weathering yellow 

 to hard flags weathering brown, suggests the possibility of a litho- 

 logical correlation. Also in the above-mentioned region Climaco- 

 graptus normalis was almost the only fossil found in the lower 

 beds of the zone of Monograptus atavus. However, this evidence 

 for the age of the beds is very slender, and we do not feel that it 

 is sufficient to enable us to separate them off from the Llathige 

 Mudstone Series. 



(C) The Llansawel Group. 



(C x ). — The Llansawel Beds are best seen along the hill-road 

 leading northwards from Llansawel to Lampeter. The road rises 

 immediately on leaving the village, and the first exposure occurs 

 in the bank 500 yards up. At this point the rise becomes more 



Q. J.G. S. No. 263. 2f 



