136 Reports and Proceedings — Geological Societij of London. 



2.— January 27, 1909.— Professor W. J. Sollas, LL.D., Sc.D., F.E.S., 

 President, in the Chair. 

 The following communications were read : — 



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

 (Communicated by Dr. J. E. Marr, F.R.S., F.G.S.) 



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 

 Cyrtograptus si/mmetriciis. 

 Monograptus riccartonensis. 

 Cyrtograptus ■miirchisoni . 

 ' Monograptus cremilatiis. 

 Mu7iograptus crispus. 

 Rastrites maximus. 

 Monograptus sedgwicki. 

 Monograptus gregarius. 

 Mesograptus modestus. 



Salopiax. 



Valentiax. " 



Benarth Flags and Grits 



Gyffin Shales. (300 feet. 



ASHGILLIAN. 



Caradocian. 



. Conway Castle Grits. 

 Deganwy Mudstones. 



(150 feet.) 

 (30 feet.) 



Bodeidda Mudstones. (350 feet.) 



Caduant Slates (Upper) . 

 Llandeilian. \ Cadnant Slates (Lower). (310 feet.) 



Conway 

 Mountain 

 Volcanic 



Series. 



J Fhacops mucronatus and 

 t Dicellograptus anceps. 



Trinncleiis Beds. 

 C Dicranograptus clingani. 

 \ Cliniacngraptm ivilsoni. 

 Dicratiograptus hrevicaulis 



and Mesograptus multidens. 

 CUmacograptiis peltifer. 

 ' Upper or Coetmor Ash Group. 

 Upper Brecciated Lava Group. 



(710 feet.) 

 Lower or Bodlondeb Ash Group. 



(60 feet.) 

 Lower Banded Lava Group. 



(1,400 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. Tbe 

 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 Conwaj^ Mountain Yolcanic 

 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 Dicratiograptus Shales, Trinucleus Beds, and 

 Sholeshook Limestone of South Wales, the Sleddale and Boman 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 possible 

 between the graptolitic zones of the Gyffin Sliales and corresponding 

 beds at Bhayader, Tarannon, in the Lake District, and the South of 

 Scotland. Finally, the Benarth Flags are compared with the Brathay 

 Flags, the^Biccarton Beds, and beds above and including Cyrlograptus 

 murchisotii in the Tarannon district. 



