﻿Vol. 64.] BALA AND LLANDOVEEY ROCKS OP GLYN CEIEIOG. 593 



Llandovery and the Tarannon Shales ; but it should be remembered 

 that in such homogeneous unfossiliferous slates, showing little or 

 no trace of bedding, it would be difficult to detect any break in the 

 succession. 



We do not propose to attempt any correlation of the British 

 deposits with those of other countries ; but reference may here be 

 made to an important paper by Dr. Kiaer ^ on the Norwegian Stage 5. 

 This corresponds with the upper portion of the Bala Series, and it 

 is divided by him into (5fl^)the uppermost Chasmops-Beds, and (56) 

 the Meristella-crassa Beds. The latter are followed by the Silurian, 

 beginning with the zone of Pentamerus undatus. 



In discussing the correlation of the' Norwegian deposits, Dr. Kiaer 

 points out that the fossils which we formerly recorded from the 

 Giyn Grit are almost all Bala forms ; and, as we identified the Glyn 

 Grit with the Corwen Grit, he places the boundary between the 

 Ordovician and the Silurian above the Corwen Grit instead of below 

 it. As we have already stated, the more detailed examination of the 

 Glyn area has led us independently to the same conclusion, so far 

 as the Glyn Grit is concerned ; but we are not certain that the Glyn 

 and Corwen Grits are identical. 



The Meristella-crassa Zone does not appear to be present in the 

 Glyn-Ceiriog District ; but it is clear that the Fron-Frys Slates 

 represent the Pentamerus-undatus Zone, which Dr. Kiaer takes as 

 the base of the Silurian System. 



EXPLANATION OF PLATE LIII. 



Gi-eological map of the country around Gljn Oeiriog, on the scale 

 of 3 inches to the mile. 



Discussion. 



The President expressed his sense of the importance of detailed 

 work, such as that so successfully accomplished by the Authors, in 

 well-selected areas. The Authors were to be congratulated on their 

 choice of an area, for it was one which had called forth the enthu- 

 siasm of Sedgwick, who, in a letter to Phillips, written in 1843, 

 spoke of it as full ' of the most beautiful geology he had ever seen 

 in his hammering life.' The Authors' views seemed to be in 

 harmony with those expressed by Sedgwick at that time, since he 

 also had regarded the black slates at the village of Ceiriog as the 

 base of the system (Upper Silurian), and had divided the Cambrian 

 (Sedgwick) into five zones. 



The Secretary read the following extracts from a letter received 

 from Mr. J. Lomas : 



' I wish to congratulate the Authors on their attempt to reduce the Glyn rocks to 

 their proper succession. No better district could have been selected to serve as a 

 type of the peripheral series of the Berwyn dome. 



' The Authors evidently incline to the opinion that the igneous bands in the 



1 ' Faunistische Uebersicht der Etage 5 des norwegischen Silursystems ' 

 Videnskabsselskabets Skrifter, I. Math.-nat. Klasse, 1897, No. 3. (Kristiania.) 



