4*5 6 ME. A. WADE ON THE LLANDOVERY AND [Aug. I9H^ 



(3) Butting ton Shales. — The igneous rock intruded at Cefn 

 forms a well-marked and isolated feature there. On the eastern 

 side of the hill, the Buttington Brickworks Company have made a. 

 large quarry in a series of green and purple shales, with which 

 are interbedded a few bands of hard green flags. About 300 feet, 

 of nearly vertical strata are exposed, but a careful search through 

 the series yielded nothing beyond a few obscure ostracoda. From 

 the position and lithological character of the strata, they would, 

 appear to be the equivalents of the Tarannon Shales. They crop out 

 nowhere else in the district, whence it may be inferred that they 

 either thin out westwards, or are overlapped by the succeeding 

 Wenlock Shales : the former alternative seems the more probable.. 

 The beds exposed in the quarry show beautifully the effects of ' creep' 

 at the surface (see PI. XXXIV). 



(4) Wenlock Shales (eastern facies.) — At Belan, south 

 of Powis Castle, hard flags and mudstones containing fossils which 

 indicate the lowest Wenlock zones seen in this area, are faulted 

 against the Llandovery conglomerate. The beds weather brown,, 

 and are cleaved and well jointed, wherefore some care is necessary 

 to distinguish the bedding-planes. Graptolites are to be found only 

 on the edges of splinters. At the top of the hill, the Wenlock is 

 overlain by the Lower Ludlow Shales, which now come against the 

 fault that runs in a direction slightly transverse to the strike of 

 the beds. 



The beds are overlain by drift in the neighbourhood of Powis Park,, 

 but crop out again to the north of Welshpool, where they are best 

 seen in Cwm Caethro, a small valley between the farms of Caethro 

 and Lower Gungrog. Here the beds are much faulted and crumpled, 

 with some evidence of overthrusting. Despite this disturbance, 

 three well-defined Wenlock zones can be established (fig. 5, p. 437). 

 The outcrop of the beds is very narrow, compared with that of 

 the overlying Silurian ; but no reliable estimate can be formed of 

 their thickness. They consist of earthy mudstones and blue flags. 

 The Cyrtograptus-linnarssoni Zone is probably concealed by faulting,, 

 while the zones of C. murchisoni and C. symmetricus usually seem 

 to be absent in this part of the Welsh Borderland. Against these 

 beds, by a small waterfall in the stream, come Lower Ludlow 

 Shales, bearing Monograptus varians and M. vulgaris, the whole 

 of the beds being crumpled and overfolded at the junction. 



Prom Cwm Caethro, the series can be traced into Trelydan 

 Dingle, at the head of which, just under Trelydan Cottage, strata of 

 Wenlock age are to be seen folded into an anticline against the 

 Trilobite-Dingle Shales. At first sight, the appearance suggests 

 Llandeilo Flags, cropping out from under the Dicranograptus Shales; 

 but the paheontological evidence proves the existence of a great fault 

 at this point. The beds consist of a blue earthy limestone, con- 

 taining in places numerous little cubes of pyrite, overlain by hard,, 

 calcareous, gritty flags. Only the limestone-band yielded fossils., 



