The Conway Succession. 



Ill 



January 27th, 1909.— Prof. W. J. Sollas, LL.D., Sc.D., F.R.S., 



President, in the Chair. 



The following communications were read: — 

 1. ' The Conway Succession.' By Miss Gertrude L. Elles, D.Sc. 

 In this area the author has found a complete succession of strata, 

 from Llandeilian up to Salopian date. The divisions proposed are 

 as follows : — 



Zone of 

 f Cyrtograptus symmelricus. 



Salopian. Benarth Flags & Grits -^ Monograptus riccartonensis . 



[ Cyrtograptus murchisoni . 

 ( (Monograptus cremdatus. 



| Monograptus crispus. 



Gyffin Shales. (300 feet.) J &***" maximus. ■ 



J v j Monograptus sedgwicki. 



| Monograptus gregarius. 

 y Mesograptus raodestus. 

 \ Conway Castle Grits. (150 feet.) 



Valentian. \ 



ASHGILLIAN. 



DeganwyMudstones. (30 feet.) { **%?*» muc ™natMs & 

 ° J ' [ JJicdlograptus anceps. 



Bodeidda Mudstones. 



Trimccleus-Beds. 



Caradocian. 



Conway 

 Mountain 

 Volcanic 



Series. 



(350 feet.) 



i Cadnant Slates ( Upper). { ^anograptus clingani. 



1 v 1 1 / y Chmacograptiis wilsoni. 



T f Cadnant Slates (Lower). I ^ranograpU^ brevicaulis & 



Llandeilian. \ /oVq * , \ i Mesograptus multidens. 



1 ^ ' " '' [ Climacograptns peltifer. 



( Upper or Coetmor Ash-Group. 



j Upper Brecciated Lava-Group. 

 | (710 feet.) 



i Lower or Bodlondeb Ash -Group. 



(60 feet.) 

 I Lower Banded Lava-Group. 

 L (1400 feet.) 



After references to the literature and an account of the 

 landscape and structure of the district, the beds are described 

 in ascending order, lists of fossils being given from the more 

 important exposures. The sections show that there is no break 

 whatever in the sequence between the Ordovician and the Silurian 

 rocks in the district. Petrological notes on the chief igneous rocks 

 are given, and then a detailed comparison is established between 

 the rocks of this area and those of South Wales, the Rhayader 

 and Tarannon districts, Lakeland, the South of Scotland, and 

 Pomeroy. The Conway Mountain Volcanic Series appears to be 

 equivalent to the Borrowdale volcanic rocks of the Lake District, 

 and the Cadnant Slates and Bodeidda Mudstones equivalent to 

 the Upper Dicrcmograptus-Shales, Trinucleiis-~Beds, and Sholeshook 

 Limestone of South Wales, the Sleddale and Roman Fell Groups of 

 Lakeland, and the Upper Glenkiln and Lower Hartfell of the 

 South of Scotland. The Deganwy Mudstones are paralleled with 

 the Redhill Beds and the Ashgill Shales. Close comparison is 



