L 155 ] 



IX. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from vol. xlviii. p. 572.] 



November 22nd, 1899.— W. Whitaker, B.A., F.R.S., President, 

 in the Chair. 



HPHE following communications were read : — 

 -*- 1. ' On some Remarkable Calcisponges from the Eocene Tertiary- 

 Strata of Victoria (Australia).' By George Jennings Hinde, Ph.D., 

 F.R.S., F.G.S. 



2. ' The Silurian Sequence of Rhayader/ By Herbert Lap worth, 

 Esq., F.G.S. 



This paper opens with a general reference to the Ordovician and 

 Silurian complex of Central Wales, and a notice of the geological 

 work hitherto done in the region. The stratigraphical relations of 

 the Silurian formations which occur in the country surrounding the 

 town of Rhayader (Radnorshire) are then described in detail. Typical 

 and confirmatory sections are given, demonstrating the complete 

 local sequence of the rocks of the Rhayader district. These are 

 illustrated by lists of characteristic graptolites. These fossils are 

 compared with those of Southern Scotland, Sweden, and North Wales, 

 showing that the graptolite-succession is everywhere similar, and 

 fixing the age of the Rhayader Series as representing the Lower 

 Llandovery, "Upper Llandovery, and Tarannon of other areas. 

 Finally, several new species of Climacograptus and JHplograjptus 

 are described. 



The author establishes the following sequence : — 



Rhayader Group (Pale Shales). 



= Gala and Tarannon 

 Group. 



^5< 



Gafallt Beds. 



^ S 1 Caban Con- 



TO C I 



glonierates. 



Gafallt Shales. 

 M. SedgwicM-grits. 

 Upper Conglomerate. 

 Intermediate Shales. 

 Lower Conglomerate. 



1 



I =Upper Llandovery, 

 )■ May Hill, and 

 | Upper Birkhill. 



Gigrin 

 Mudstones. 



& Ddol Shales. 



Pale Grey Mudstones. 

 Zone of M. convolutus. 

 Calcareous Nodule-beds. 

 [ Zone of M. fimbriatus. 

 \ ,, M. cyphus. 

 Sci { „ M. tenuis. 



go DyfFryn \ S' ' T d f ^"ST 



O Flaes 1 R° ttens tone Beds. 



^ ' [ Micaceous Flags & Grits 

 Cerig Gwynion 

 L Grits. 



Blue-black Shales. 



:Lower Llandovery 



and 



Lower Birkhill. 



:Bala and Hartfell. 



No single section, taken in any direction across the Rhayader 



