OUTLIER OF CLUN FOREST. 191 



downwards into rocks containing, the characteristic fossils of the Ludlow formation. 

 There are, however, overlying thicker-bedded sandstones and micaceous, red and green 

 spotted marls, which are deeply cut into by ravines near Hall in the Forest, above New- 

 castle, also near Bettws, and these may be referred to the central members of the for- 

 mation, though I never observed any traces of real cornstone 1 . The ridge of Silurian 

 rocks in which the Teme rises, and which separates that river from the valley of the 

 Ithon, is the southern prolongation of Kerry Hill, and is composed of grey-coloured 

 masses, which offer numerous sections, proving them to belong to the Ludlow formation. 

 The strata, dipping to the east, pass under the flaggy beds of Old Red, and contain 

 many fossils, which, as will hereafter be shown, are characteristic of the upper Ludlow 

 rock, and are never found either in older or younger formations. (See tabular view, 

 locality, Felindre, &c.) From these beds of upper Ludlow rock, there is as true a pas- 

 sage upwards into the 'tilestone' or "firestone" beds, as any exhibited in Caermar- 

 thenshire, Brecknockshire, or Herefordshire. The passage beds near Felindre are hard, 

 greenish, and reddish, highly micaceous sandstone, which contain the Leptcena lata and 

 the Terebratula Nucula of the Ludlow rock (PL 5.), together with casts of several shells, 

 identical with those found in the tilestones of the Cwm Dwr, Caermarthenshire, and 

 which have never been found in the Silurian System below its junction with the Old 

 Red Sandstone. These fossils are represented in PI. 3, the lower part of which in par- 

 ticular, is occupied by figures of the remains occurring in the beds of passage between 

 the Old Red and Silurian Systems. (See subsequent description of these fossils and 

 some remarks thereon.) The casts of these fossils, though in a very fragile state, are 

 beautifully preserved, the cavity between the mass of the rock and the casts of the 

 shells being generally filled with a black powder, probably a mixture of silex and 

 iron. 



The tilestone beds, (firestone,) exhibit sometimes thin layers jof matted and broken 

 vegetable remains, frequently in a state of impure carbon. These vegetable fragments 

 are found in quarries three miles north of Knighton on the road to Clun ; and at Rhyd- 

 cwm near Felindre. The plants are conjectured to be terrestrial, but are in too mutilated 

 and broken a condition to be referred to any known genera, fossil or recent. 



Outliers of Old Red Sandstone in Radnorshire. 



Norton. — The outlier next in magnitude to that of the Forest of Clun, is situated be- 

 tween Presteign and Knighton, and covers an area of about five square miles. This 



1 I am indebted to Mr. Mickleburgh, land- surveyor, of Montgomery, for much assistance in laying down the 

 outline of this wild tract upon the map. Mr. Mickleburgh is most intimately acquainted with the diversity of 

 soils ; the natural drainage ; in short, with the physical geography of his native county. I have had repeated 

 occasions of testing this knowledge in the field, not only in the mountain tracts of the Forest of Clun, but also 

 in the complicated and broken districts around Hyssington and Shelve. 



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