306 



Prof. Sedgwick on the May Hill Sandstone, 



feet, inasmuch as not one of them shows a perfect and continuous 

 sequence of all the deposits within the limits of the section, and 

 I have never seen any such perfect section in North Wales*. 



Fig. 1. 



Denbigh flag 



(Wenlockand 



Ludlow). 



May HiU 

 sandstone, &c. 



Conglomerate. 



Fig. 3. 



Earthy slates. 



Calcareous 

 beds and con- 

 glom«rate. 



Limestone of 

 Meifod. 



Slates, &c. 

 not exposed 

 in the section. 



""• III .__! 



Paste-rock. 



Upper lime- 

 stone. 



Lower lime- 

 stone. 



Slates and 

 porphyries, 

 &c. alterna- 

 ting. 



Three sections representing the junction of Cambrian and Silurian rocks 

 in North Wales. 



Fig. 1. From the neighbourhood of Cemiogie on the Holyhead road, 

 where the May Hill group (No. 2) is largely developed, and rests uncon- 

 formably upon a part of the Upper Bala group (No. 1), and is surmounted 

 conformably by the Denbigh flag (Wenlock, &c.) (No. 3). 



Fig. 2. From Mathyrafsd. Here the Upner Bala group (No. 1) has an 

 unusual mineral type, and is overlapped. with a slight discordancy of posi- 

 tion by the Wenlock series (No. 3). The May Hill series (No. 2) is 

 entirely wanting. 



Fig. 3. From Glyn Ceiriog, south of Llangollen. Here a portion of the 

 Upper Bala group (No. 1) is overlaid, without any apparent discordancy of 

 position, by the Denbigh flag (No. 3) j but the May Hill group (No. 2) is 

 entirely wanting. 



* I believe, however, that some rather soft earthy slates (seen at Glyn 



