192 THE OEDOVICIAN AKD SILUEIAN EOCKS OF CONWAY. [May I909, 



In conclusion, I wish to acknowledge my indebtedness to my 

 friend Mrs. Shakespear, who has allowed me to make free use of all 

 the notes and observations made by us jointly during the progress of 

 our earlier work. My friend and pupil Miss E. G. Welch has also 

 assisted me, both in the field in mapping the Volcanic Series, and by 

 furnishing me with notes on the lavas from which the description 

 of these rocks was drawn up ; to her and to Mr. 0. T. Jones, who 

 has helped me in the correlation of the beds, I offer my grateful 

 thanks. I wish also to acknowledge the assistance that I have 

 received from Mr. Alfred Harker, Mr. W. G. Fearnsides, and Mr. It. 

 H. Eastall in the interpretation of the rock-slices, the results of 

 w 7 hich are embodied in the last section of this paper. 



EXPLANATION OF PLATE VIII. 



Geological map of the neighbourhood of Conway, on the scale of 3 inches to 

 the mile ; and section on the west side of the River Conway, on the scale 

 of approximately 6 inches to the rniie. 



Discussion. 



Mr. H. H. Thomas congratulated the Author on the excellent 

 way in which she had disentangled the structure of a complicated 

 district, and once again presented to the Society a detailed account 

 of a most important geological succession : work made possible 

 and doubly valuable by her knowledge of palaeontology. It was 

 most satisfactory also when the age of a volcanic series could be 

 so accurately defined as it had been in the present instance. 



With regard to the DicranograjitusShales, he remarked on the 

 advantage that he had received from the Author visiting with him 

 some of the chief sections in South Wales. He commented on the 

 remarkable lithological resemblance offered by the shales at Conway 

 to those in Caermarthenshire, where the same lithological changes 

 occur with the same faunal difference. While agreeing perfectly 

 with the Author as regarded the line which should be taken as 

 dividing Glenkiln from Lower Hartfell, he felt that this line could 

 not logically represent the division between Llandeilo and Bala. 

 At Llandeilo the Llandeilo Flags were the only rocks that could be 

 included in Murchison's Llandeilo Formation, the Dicranograptiis- 

 Shales which occurred above belonging naturally to the Bala. The 

 shales above the Llandeilo Flags at Llandeilo contained exactly the 

 same fauna as the shales described by the Author as occurring 

 above the Conway Volcanic Series. The speaker recognized that 

 there were difficulties in the way, but suggested that the dividing- 

 line between Llandeilo and Bala should, in the Conway district, be 

 drawn at a lower horizon than that indicated in the paper. 



Mr. W. Whitakee asked whether the correlation of the Conway 

 Grits with the Hirnant Limestone depended only on palseontological 

 evidence, or whether continuity of the beds had been traced. 



