10 P. C. DA. VIES ON THE UPPER CARBONIFEROUS 



2. On the Relation of the Upper Carboniferous Strata of Shrop- 

 shire and Denbighshire to Beds usually descnbed as Permxan. 

 By D. C. Davies, Esq., F.G.S. (Read June 21, 1876.) 



[Plate L] 



The strata I am about to describe occur in the north-west corner of 

 Shropshire and in the adjacent south-east corner of Denbighshire. 

 They are cut through by the rivers Ceiriog and Dee ; and a good sec- 

 tion of a portion of them may be seen along the bauks of the Dee, 

 from the mouth of the Ceiriog downwards towards Erbistock. 



I directed attention to these beds in the year 1873 *. Since that 

 time I have been engaged constantly in colliery operations in the 

 district and strata then referred to ; and I propose in this communi- 

 cation to narrate the results of my observations during the interval, 

 and also to inquire into the relative position of these strata with 

 others which are usually described as Permian. 



The order of the beds and their relation to the underlying Coal- 

 measures will be understood by a reference to the horizontal sec- 

 tion which accompanies this paper (PI. I. B). This section extends 

 from the Brynkinallt Colliery, near Chirk, on the west, past the new 

 sinkings of the Ifton-Rhyn Collieries on the east. The line of the 

 section was carefully surveyed by Mr. E. B. Henderson, E.G.S. ; and 

 the geological details are supplied by the section of the Brynkinallt 

 Colliery on the west, the Hafod-y-bwch pit-section on the north, 

 the recent sinkings and borings at Ifton on the east, taken together 

 with the outcrops of the strata which are visible along the line of 

 the section. 



Section no. 11, of the Diagram of Sections (PI. I.), gives in a con- 

 densed form the details of the strata to be described from the Spi- 

 rorbis -limestone upwards. 



Prior to the year 1873 this limestone had not been recognized in 

 the North- Shropshire and North-Wales coal-field. Early in that 

 year I was taken to see some supposed ironstone beds in the Pentre- 

 Isaf ravine, near Wynnstay. I was struck with the calcareous 

 nature of these supposed ironstones ; and upon a close examination 

 I observed the little spiral shell, Spirorbis carbonarius, together with 

 another minute shell which Mr. Etheridge, to whom I submitted 

 a specimen of the limestone, regards as Cythere scotoburdigalensis. 

 Both Mr. Etheridge and Mr. Daniel Jones, E.G.S., who has paid 

 much attention to the yS^Vorfo's-limestone in South Shropshire and 

 the Eorest of Wyre, confirmed me in the conclusion I came to, that 

 the supposed ironstone beds were none other than the Spirorbis- 

 limestone itself. I may on a future occasion describe these lime- 

 stones and their associated strata more minutely ; at present I 

 would simply add that in February of this year the same limestones 

 were passed through in the No. 3 pit, at Ifton-Bhyn Collieries on 



* " On Coal-seams in the Permian at Ifton, Shropshire," Proceedings of the 

 Geologists' Association, vol. iii. no. 3. 



