22 



MR. PHILIP LAKE ON THE DENBIGHSHIRE [Feb. 1895, 



Upper Gritty Beds have yielded no fossils, it is clear from their 

 position that they correspond with the Coniston Grits. 



Above the Coniston Grits come the Bannisdale Slates, in which 

 Mr. Marr has obtained Monograptus leintwardinensis, M. Sdlweyi, etc., 

 and these must therefore correspond in part with the Leintwardinensis- 

 beds of Pen-y-vivod. 



It is not easy to determine precisely what part of the Lake 

 District sequeDce corresponds with the Dinas Bran Beds. The 

 abundance of Dayia navicula in the latter might suggest that they 

 represent the passage-beds between the Bannisdale Slates and the 

 Kirkby Moor Flags ; but this species is not by any means limited to' 

 that horizon. The position of the Dinas Bran Beds, however, forces 

 us to place them either at the top of the Bannisdale Slates or in the 

 Kirkby Moor Mags ; and the fossil evidence certainly does not' 

 oppose this view. 



Approximative Correlation oe the Wenlock and Ludlow Rocks 

 on the Welsh Borders, in North Wales, and in the Lake 

 District. 



Welsh Borders. 



North Wales. 



Laee District. 



S3 



c3 



g< 

 O 



B 



cj 



ft. 

 O 



03 



m 



( Downton Sandstone. 



Upper Ludlow Shales. 



Ayrnestry Limestone. 

 v Leintwardine Flags. 



f 



Lower Ludlow Shales. 



Wenlock Limestone. 

 v Wenlock Shale. 



Dinas Bran Beds. 



Leintwardinensis-beAs. 



Upper gritty Beds. 



Nantglyn Flags. 

 Moel Ferna Slates and 

 Pen-y-glog Grit 



Pen-y-glog Slates. 



Kirkby Moor Flags. 

 Bannisdale Slates. 



Coniston Grits. 



Upper 1 



Middle I OoldwellBeds. 



Lower J 



Brathay Flags. 



VII. Conclusion. 



It will be clear, upon the face of the foregoing evidence, that 

 the Denbighshire series is by no means the abnormal development 

 of the Silurian which it is sometimes represented to be ; but that, 

 on the other hand, it belongs to the most widely-spread facies of 

 that system in England. The beds of limestone, with their peculiar 

 faunas, which occur in the Silurian of the Welsh borders, are not 

 found in North Wales and the Lake District; but if these be left 

 out of consideration, the sequence is very similar iu the three areas. 



Moreover, the Denbighshire series does not correspond with the 

 Wenlock only, as is frequently stated. It contains representatives 

 of the Ludlow, and indeed of the Upper Ludlow. It is only the 

 uppermost beds of the latter which appear to be absent. 



