﻿548 DR. T. GROOM AND MR. P. LAKE ON THE [NoV. I908, 



1879, E.Etheridge. ' On the Occurrence of the Genus Ramipora (Toula) in 

 the Caradoc Beds of the Neighbourhood of Corwen ' Geol. Mag. 

 dec. 2, vol. vi, pp. 241-44 & pi. Ti. 



1885. Thomas Euddy. ' List of Caradoc or Bala Fossils found in the Neigh- 

 bourhood of Bala, Corwen, & Glyn Ceiriog' Proc. Chester Soc. Nat. Sci. 

 pt. iii, pp. 113-24. 



1885. Gc. W. Shrubsole. ' Note on Glauconome disticha, from the Bala Beds 

 of Gljn Ceiriog ' Proc. Chester Soc. Nat. Sci. no. 3, pp. 98-100. 



1893. P. Lake & T. T. Groom. 'The Llandovery & Associated Rocks of the 

 Neighbourhood of Corwen ' Quart. Journ. Geol. Soc. vol. xlix, pp. 426- 

 39; with map & sections. 



1893. T. H. Waller. 'Note on a Rock from Glyn Ceiriog' Midland Natu- 



ralist, vol. xvi, pp. 201-204. 



1894. T. McKenny Hughes. ' Observations on the Silurian Rocks of North 



Wales' (paper read in 1886) Proc. Chester Soc. Nat. Sci. no. 4 



(1894) pp. 141-60, with two sections. 

 1897. JoHAN Ki^R. ' Faunistische Uebersicht der Etage 5 dea norwegischen 



Silursystem ' Videnskabsselskabets Skrifter : i. Mathematisk-naturv. 



Klasse, 1897, No. 3. (Eiristiania.) 

 1904. T. H. Cope & J. Lomas. ' On the Igneous Rocks of the Berwyns ' 



Rep. Brit. Assoc. 1903 (Southport) pp. 664-65. 

 1904. Thomas H. Cope. • Types of Rock-Flow in the Ceiriog Yalley & their 



Analogies with River-Structure' Proc. Liverpool Geol. Soc. vol. ix, 



pt. 4, pp. 303-31. 



The earliest account of the geology of the district with which we 

 are acquainted, is to be found in Bowman's paper on the Silurian 

 rocks of the Yale of Llangollen. That author is concerned chiefly 

 with the Silurian beds ; but he also describes in some detail the 

 igneous rocks of the Ceiriog, and comes to the conclusion that they 

 are intrusive. He seems to consider the crag which overlooks 

 Pandy (' Pen y Graig ' of his paper) as a neck through which the 

 igneous rocks have been poured. 



But by far the most important of the earlier references to the 

 district are those in Sedgwick's paper on the older Palaeozoic rocks 

 of North Wales. Unfortunately the published abstract is somewhat 

 brief, and the sections, three of which pass through this region, are 

 on a scale too small to show the details of the succession. Both the 

 abstract and the sections were prepared by Warburton from the 

 original manuscript, and Sedgwick states that they do not fairly 

 represent his views, and that he himself cannot understand the 

 sections.^ It is clear, however, that in this neighbourhood he 

 recognized three main subdivisions in the rocks which are coloured 

 as Bala on the Geological-Survey map, namely : (1) a lower group 

 formed by the beds south of Pont-y-Meibion ; (2) a middle group full 

 of fossils, and containing several bands of contemporaneous volcanic 

 rock; and (3) an upper group, including the two well-known lime- 

 stones, which are placed by Sedgwick high above the Bala Lime- 

 stone. The third group 



'passes upwards into pale-coloured earthy slates and these seem to pass, 

 without a break, into the overlying Denbigh flagstone.' (Quart. Journ, Geol. 

 Soc. vol. i, 1845, p. 14.) 



Subsequently he came to the conclusion that the upper series is not 



^ Preface to Salter's ' Catalogue of the Collection of Cambrian & Silurian 

 Fossils contained in the Geological Museum of the University of Cambridge' 

 1873, p. xxvii. 



