Vol. 50.] ANNIVERSARY ADDRESS OF THE PRESIDENT. 8 1 



the Eycott and Rhyolitic groups and of the principal varieties of 

 intrusive rocks, yet the chief interest of the paper, for my present 

 purpose, centres in the heds that lie above the Rhyolitic group. 



Succeeding the rhyolite of Knock Pike, which may be regarded 

 as representing the higher portions of the Volcanic Series within 

 the area, are some layers of fine, apparently unfossiliferous ashes, 

 which pass up into calcareous shales with nodular masses of lime- 

 stone crowded with fossils, some of the calcareous bands being 

 composed exclusively of the valves of Beyrichia. One bed of the 

 series having previously been spoken of as the Discina (Trematis) 

 corona-bed, the Authors propose to name the whole the Cortma-series. 

 This is interesting from the fact that it seems to be older than 

 anything which has been referred to the Coniston Limestone group in 

 the Lake District proper. The fauna is a very marked one, entirely 

 different from that of the ordinary Coniston Limestone, nor has any 

 similar fauna been hitherto recorded from the British Islands. 

 The next beds in ascending order are the Dufton Shales and 

 Keisley Limestone, which are held to be referable to the same sub- 

 division, notwithstanding their lithological dissimilarity. Most of 

 the Dufton Shale fossils are said to be common in the Coniston 

 Limestone, the Bala Limestone, and the Trimicleus-shalea of 

 Sweden; and the Authors hold that the Dufton Shales, if not 

 actual representatives of the Coniston Limestone, are far more 

 closely allied to it than to the underlying Corona-beds with which 

 they have hitherto been associated. The group of fossils in the 

 Keisley Limestone is essentially that of the Coniston Limestone, but 

 there are some curious differences. The Staurocephalus-limestone 

 and the Ashgill Shales complete the column of the Coniston Lime- 

 stone series, and, as we have already seen, are regarded by the 

 Authors as constituting the summit of the Ordovician system. The 

 whole, including the Rhyolitic group, is regarded as of Bala age, 

 the term being used as synonymous with Caradoc, so that the 

 Lower Bala of that district in the sense used by the Authors is not 

 Llandeilo. 



Turning our attention now to North Wales, we have lately had 

 a paper on the Llandovery and associated rocks of the neighbour- 

 hood of Corwen by Messrs. Lake and Groom. It seems to have 

 been for some time a doubtful point whether true Llandovery rocks 

 are represented in the northern part of Wales ; but in 1877 Prof. 

 Hughes concluded that the grit at Corwen is of Llandovery age, 

 and that it forms the base of the Silurian in this area, which includes 



