part 2] PALEOZOIC eocks of the llangollen disteict. 181 



r 5. 



Table T (cont.). 

 P e n - y - g r a i g Ash. P e n - 3-^ - g r a i g Ash? 

 Thin keratophyric ash, Not observed west of 



only found 

 tervals. 



at in- Tomen-jf-bwlch. 



Dark-blue slates. 



3. 





B r y n B e d s . 



Dark-blue slates and 

 argillaceous, siliceous, 

 and ashy sandstones, 

 thin ashes and con- 

 glomerates. 



Sills of lime-bos- 

 tonite in places. 



Homalonotus bisulca- 

 tus, Trinucleus con- 

 centricus, Orthis 



eleganttda (largo), 

 Fhacops apiculatus. 



PandyAsh. PandyAsh, 



Agglomeratic, coarse and fine-grained kerato- 

 phyric tuff, with occasional blocks of kerato- 

 phyre. Very variable in thickness. 



2. 



T e i r w Beds. 



(b) Rather unfossiliferous 

 slates and thin, often 

 uncleaved sandstones, 

 with some thin bauds 

 of ash. 



Teirw Beds. 



Practicallj' unfossili- 

 ferous shales and 

 sandstones, with a 

 thick double band of 

 ash incoi'porating 

 pebbles of shale, ir. 

 the middle of the 

 series (Swch - Gorge 

 Ash). 



(a) Massive sandstones 

 with Glyptograptus 

 teretiusculus and 

 Calymene (?) plani- 

 marginata, Asaphus 

 poivisi, Trinucleus 

 concentricus. 



1. Cwm-clwyd Ash. Cwm-clwyd Ash. 



Massive and well-bedded, almost platy kerato- 

 phyric ash, coarse or fine in grain. 



