Vol. 65.] THE ORDOVICIAN AND SILURIAN ROCKS OP CONWAY. 193 



Mr. J. Hopkinson said that he had been greatly interested in 

 the paper, as he had many years ago collected graptolites from the 

 black shales in the area described by the Author, then concluding 

 from their evidence alone that the lower beds were of Llandeilo age. 

 This the Author had now proved from the general succession of 

 the strata which she had so well worked out and so lucidly brought 

 before them, as well as from her intimate knowledge of the grapto- 

 lites by which she had been enabled to make out in detail the 

 succession of the fossiliferous strata. The Society was much 

 indebted to her, for bringing before it the results of her investi- 

 gations in a district of great geological interest. 



Prof. W. W. Watts congratulated the Author on* having found a 

 section in Wales which bridged over the gap between the Ordovician 

 and the Silurian rocks, thus showing the palseontological character 

 of beds very little known elsewhere. The Author had also 

 contributed a very important piece of evidence with regard to the 

 position of the volcanic members of the series in Wales. In this 

 connexion, he recalled Mr. Harker's placing of the Conway volcanic 

 rocks very low down in the Snowdonian Series. He referred 

 to the Hartfell-Glenkiln fauna, which, divided into two distinct 

 horizons in Scotland, presented a union at many localities in Wales 

 and the Borders. 



Mr. E. A. Martin congratulated the Society on the excellent 

 paper which a lady-geologist had placed before them. 



The President (Prof. Sollas) remarked on the great interest 

 of this paper, especially in its relations to general questions. The 

 concordant sequence of the strata of the two systems described 

 should not, he thought, be identified with conformity. The great 

 break at the base of the Silurian, which was so marked a feature 

 in South Wales, and in many parts of the world more remote, 

 was probably not so much absent at Conway as not apparent. 

 The inconsiderable thickness of the two series, as measured by the 

 Author, by itself suggested a lapse of stratigraphically unrecorded 

 time. These deceptive conformities presented a problem of great 

 interest, which still awaited solution. 



The Author in reply thanked the President and Fellows of the 

 Society for their generous appreciation of her work. With regard 

 to the points raised by Prof. Watts and Mr. Thomas as to the age 

 of the different members of the Dicranograptus-Shdles, the beds 

 were considered to be Lower Hartfell where the large Diplograpti 

 (Orthograpti) came in, in great numbers ; and this was a very easy 

 horizon to recognize in the field, without any special knowledge 

 of graptolites. Below these were beds constituting a passage- 

 zone, characterized by Dicranograpius brevicaulis and Mesograptus 

 multiclens ; in the lower parts of the zone, the fauna showed decided 

 Glenkiln affinities, while in the higher there was indication of the 

 incoming of the lower Hartfell fauna. The beds below this zone 

 contained a decided Glenkiln fauna, and she was of the opinion 

 that there were serious palseontological objections to their inclusion 

 Q. J. G. S. No. 258. o 



