312 



LUDLOW ROCKS IN RADNORSHIRE. 



are overlaid on the face of the hills by courses of thin-bedded building-stone similar to that 

 at Downton Castle. On the whole these rocks are rather more micaceous than at Ludlow. 



The Lower Ludlow Rock is well seen in a transverse section north-west from Bradnor 

 to Herrock Hill, on the sides of which dull, dark-coloured, thinly laminated shale, 

 without mica, and containing nodules of argillaceous limestone, dips under the harder 

 strata of Bradnor Hill. 



The Upper Ludlow Rock is again seen all along the Hergest ridge, and thence by 

 Gladestrey to Pain's Castle, where the formation is strikingly displayed filled with well- 

 preserved fossils, and overlaid by ridges of Old Red Sandstone. In no portion of the 

 region examined are the relations of the Ludlow rocks to the overlying system more 

 clearly shown than between Pain's Castle and the Wye. The Old Red Sandstone oc- 

 cupying the Clyro and Begwn Hills is succeeded on the north-west by a series of lower 

 terraces of Ludlow rock, the beds of which all dip conformably beneath and graduate 

 upwards into the Old Red. This " terrace under terrace " is beautifully marked near 

 Pain's Castle at the escarpment of the Begwn Hills, and extending thence by Llanste- 

 phen to the Trewerne hills on the left bank of the Wye. It was here that I first ob- 

 served a passage downwards from the Old Red Sandstone into these older formations, 

 as represented PI. 31. f. 1. The beds are rich in organic remains. Among the usual 

 and characteristic fossils, the small Pleurotomaria Corallii occurs, surrounded by the 

 same species of coral which envelops the shell at Ludlow, Delbury, Larden, Botville, 

 &c, in Shropshire. The strata dip at low angles to the north-east. 



In the immediate vicinity of the Begwm Hills, the lower part of the Ludlow forma- 

 tion has been violently contorted, especially in the narrow mountain gorge in which 

 the Bach-Howey (Brach-Wye, or tributary of the Wye,) falls over a vertical cliff at 

 Craig-pwl-du. These contortions being among the most remarkable to which this 

 formation has been subjected, a sketch is annexed. 



51. 



