part 1] ON THE GEOLOGY OF THE OLD RADNOR DISTRICT. 1!) 



seen near the floor of the old quarry at the end of the railway- 

 siding, below tlje large Yat-Hill Quarry (Quarry E), and again 

 beside the footpath which runs round the south-east side of 

 the inlier, close to the stile, about 100 yards north of the 

 outcrop of Wenlock Shale in Weythel Brook. It also occurs in 

 Dolyhir Quarry, where it has been removed during quarrying 

 operations, though fragments may still be found on the floor of 

 the quarry. Traces of the same shale also occur in the old quarries 

 near Vat Farm. The bulk of the shale is much crushed and is 

 very friable : it contains a fair abundance of greenish cementstone 

 concretions, which have been formed round local accumulations 

 of crinoid-stems and young brachiopods. . This shale contains, 

 on the whole, a fauna distinct from that of the limestone,, and 

 is remarkable for the number of trilobites, gastropods, and small 

 cup-corals which it contains, and especially for the abundant 

 remains of llhenus (Bumastus) barrieusis. 



The following is a list of the fossils which have been collected 

 from this deposit : — 



Streptelasma sp., single form, abun- Cheirurus bimucronatus Murchison. 



dant. ' Dalmanites caudatus Bronn. 



Favosites forbesi Edwards & Haime. Deiphon forbesi Barrande. 



Athyris ? depressa Sowerby. Illsenus barrieusis Murchison. abun- 

 Atrypa reticularis Linnasus. dant. 



Leptsena rlwmboidalis "VYilckens. Lichas fCorydocephalu sj hirsutus (?) 

 Platyceras prototypum Phillips, Fletcher. 



abundant. Lichas (DicraaopeltisJ salteri 

 Bronteus signatus Phillips. Fletcher. 



Calymene blumenbachii Brongniart. 



The trilobites in the foregoing list, with the exception of 

 Calymene ; appear to be confined to this shale-band, and the same 

 may be said of the small cup-corals. The collections of gastropods 

 and brachiopods, as well as of trilobites, are notable for the number 

 of young forms which the}" include. The fauna, taking it altogether, 

 is distinctly Middle Silurian in character, and confirms the view 

 arrived at from a study of the limestone as to the Wenlock age of 

 the deposit generally. 



This shale appears to mark a period early in the subsidence of 

 the area, when the growth of the bryozoan reef gave rise to shallow 

 lagoons : in these fine silt was quietly deposited, and they served 

 as a nursery for numerous 3 r oung forms. 



(e) The Wenlock Shale. 



According to the Geological Survey map the inlier is entirely 

 surrounded hy Wenlock Shale, but its contact with the rocks of 

 the inlier is only seen at the present day in the section in Weythel 

 Brook already mentioned. Two small patches of this shale, how- 

 ever, occur in the inlier itself: one in Dolyhir new quarry, and the 

 other in the old limestone- workings north-east of the Harp Inn. 

 In the former case the shale has been let down and preserved 



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