CHAPTER XXV. 

 SILURIAN, CAMBRIAN, AND TRAP ROCKS IN RADNORSHIRE. 



Upper and Lower Silurian Rocks of Presteign, the Vale of Radnor, Radnor Forest, 

 fyc— Cambrian Rocks in West Radnor. — Volcanic Group and Altered Rocks 

 of Old Radnor. (PI. 33. figs. 1, 2, 3, and 4.) 



Quitting the region where the best types of the Silurian System are exhibited, let 

 us now follow these rocks upon their strike from north-east to south-west, through the 

 counties of Radnor, Brecknock, and Caermarthen, till we take leave of them in the 

 coast-cliffs of Pembrokeshire. 



In this long course of one hundred and fifty miles, I shall successively direct attention 

 to the prominent features of the system in each district, indicating specially those places 

 where the distinguishing rocks disappear and re-appear. 



We shall afterwards trace them wherever they rise from beneath the younger depo- 

 sits on the eastern side of Herefordshire, and in Gloucestershire, Worcestershire, and 

 Staffordshire. 



Ludlow Rocks on the South-eastern side of Radnorshire. — The Ludlow rocks between 

 Aymestry and Presteign occupy the ridge of Shobdon Hill and Wapley Court, but the 

 central band of limestone, containing the Pentamerus Knightii, is no longer visible ; so 

 that the Upper Ludlow is separable from the Lower only, by observing the fossils pecu- 

 liar to each, or by the harder stony character of the former, as distinguished from the 

 perishable, argillaceous structure of the latter. Thus united, the Ludlow rocks fold 

 round the north and west sides of Presteign, passing under the detached outlier of Old 

 Red Sandstone at Norton ; the upper Ludlow rock, as quarried at many places, 

 being usually charged with the same shells as in the Ludlow district. (See various 

 quarries around Presteign.) Instructive and clear sections of the Ludlow rocks are 

 again displayed in the prominent ridge extending from the beautiful high grounds of 

 Eyewood Park by Bradnor and Hergest Hills, north-west of Kington, the strata dipping 

 to the south-east at low angles beneath the Old Red Sandstone. (PL 33. f. 2.) There 

 are numerous quarries, both in the eastern face and in the abrupt western escarpment 

 of these hills, and the beds abound with the usual fossils or their casts. In the ex- 

 cavations of Bradnor Hill above Kington, many of the beds are highly calcareous, in 

 consequence of the shelly matter of these fossils, particularly Leptcena lata,Cypricardia 

 amygdalina, Spirifer ptychodes (Dalman), Orbicula rugata, Orthis lunata, &c. These beds 



2 q 2 



