283 



PROCEEDINGS, 



ETC. 



POSTPONED PAPERS. 



Contributio7is to the Geology o/" North Wales. By Daniel 

 Sharpe, Esq., F.G.S. 



Plates XII., XIII. 



[Read March 6th, 1844.] 



The author made a tour in North Wales, having two objects prin- 

 cipally in view: the first, to classify the stratified rocks of that 

 country; the second, to ascertain what are the beds that lie below 

 the Silurian rocks of Sir R. Murchison, and whether those beds con- 

 tain any organic remains. 



After first observing the structure of those parts of the country 

 where the order of superposition in the beds was already known, he 

 proceeded to examine other districts where the arrangement of the 

 rocks is more obscure and complicated. 



Upper Silurian Rocks. — Llangollen district. 



He began by studying the Llangollen district, described by the 

 late Mr. Bowman *. He agrees with that geologist in referring the 

 Upper Silurian rocks in that neighbourhood, partly to the Ludlow 

 and partly to the Wenlock series of Sir R. Murchison- 



Ludlow series. — This series, in descending order, consists of 



1. Thin, grey, micaceous beds, containing Terebratula naviculoy 

 Leptcena lata, several species of Cypricardia, and other fossils. 



2. Liver-coloured shales. 



3. Blue shale. 



The distinction which exists in the English border counties, be- 

 tween the Upper and Lower Ludlow beds, cannot here be made 

 out; nor is there any trace of the Aymestry limestone. There are 

 so few fossils in the greater part of the Ludlow and Wenlock series 

 in North Wales, that it is by diflerences of colour or mineral com- 

 position that one is often obliged to distinguish them. The Lud- 

 low series is of soft texture, is readily decomposed by weathering, 



* See Trans. Geol. Soc. Manchester, vol. i. p. 194. 



