Vol. 65.] THE ORDOVICIAN AND SILURIAN EOCKS OF CONWAY. 185 



The lowest beds, a series of flags and shales, with some harder 

 gritty bands, are seen along a road-section behind Bryn Dowsi, 

 where they are full of Mesograptus modestus (Lapw.), Climacograptus 

 normalis, Lapw.. CI. rectangularis > M'Coy ; and in the higher bands 

 Monograptus incommodus, Tornq., comes in. These are clearly the 

 Mesograptus-modestus Flags of other areas. They are seen to be 

 succeeded at once by higher shales in the small quarry north-west 

 of the farm ; the beds are somewhat disturbed here by the proximity 

 of the fault, but have yielded an unmistakable assemblage of grap- 

 tolites, namely : — 



Climacograptus rectangularis, M'Coy. 

 Climacograptus hughesii (Nich.). 

 Glyptograptus tamariscus (Nich.). 



Monograptus revolutus, Kurck. 

 Monograptus fimbriatus, Lapw. 

 Monograptus lobiferus, M'Coy. 



These clearly indicate the beds to be on the horizon of the lower 

 part of the Zone of Monograptus gregarius, Lapw. 



The lower beds are again seen on the roadway due north of Pont 

 Gyffin (1), where they are, however, much thinner ; and the higher 

 beds come up in a crumpled anticline, in a small quarry south-west 

 of Bryn Glorian Mawr (2), and in the wood to the north-west (3). 

 Here I have collected : — 



(1) Pont Gyffin. 



Mesograptus modestus (Lapw.). 

 Climacograptus normalis, Lapw. 

 Climacograptus rectangularis, M'Coy. 



Climacograptus hughesii (Nich.). 

 Glyptograptus persculptus (Salt.). 



(2) South-west op Bryn G-lorian Mawr. 



peregrinus, Barr. 

 Monograptus fimbriatus, Lapw. 

 Monograptus gregarius, Lapw. 

 Monograptus attenuatus, Hopk. 

 Monograptus jaculum (?) Lapw. 

 Monograptus communis, Lapw. 



Monograptus lobiferus, M'Coy. 

 Monograptus triangulatus (Hark.). 

 Glyptograptus tamariscus (Nich.). 

 Climacograptus scalaris, His. 

 Climacograptus hughesii (Nich.). 



(3) Wood north op Bryn Glorian Mawr. 



Eastrites peregrinus, Barr. 

 Monograptus attenuatus, Hopk. 

 Monograptus communis, Lapw. 



Monograptus triangulatus, Hark. 

 Monograptus jaculum (!) Lapw. 

 Climacograptus hughesii (Nich.). 



The only locality known to me where the Zone of Monograptus 

 sedgwicki is exposed, is at the mouth of the Afon Gyffin, due north 

 of the Lodge at the entrance to Benarth ; here certain rocks, which 

 are only exposed at the lowest spring-tides, yielded numerous 

 examples of Monograptus sedgwicki itself, with some Diplograptidse, 

 and I believe represent that zone. The succeeding beds of the Zone 

 of Rastrites maoeimus are to be seen in the river-bank beyond the 

 timber-yard a little farther west (i), and also in the bank behind 

 'the timber-stacks at the corner of the Gyffin road (ii). 



