VOL. XIX. (2) 
THE SILURIAN INLIER OF USK 
M7 
The presence of Holopella gregaria confirming the con- 
clusion, due to the neighbourhood of the Old Red Sandstone, 
that we have here the uppermost Ludlow beds. 
Further to the South the road from Llandegveth, after 
crossing the stream near Brook House, passes through a 
cutting, which at one time must have clearly shown the nature 
of the junction between the Silurian and Old Red Sandstone 
beds. At present, however, one can only see red and green 
marls, which dip 30° S.E., and brown fossiliferous Ludlow 
shales, but the actual junction is overgrown. 
Still further South yellow sandstones with a few calcare- 
ous layers are to be seen in a small stream which runs past 
Duke’s Brake, and in these Chonetes striatella, Spirifer crispus, 
and other Ludlow fossils occur. 
From the above account of the Silurian beds of the 
Llangibby Anticline, it is obvious that the same general 
succession is seen in it as is apparent in the Coed-y-paen 
Anticline. The Wenlock Limestone of the two areas is similar 
in its lithology and in its fauna, while the Ludlow beds, 
though perhaps they show less frequent layers of calcareous 
nodules in their lower parts in the Eastern Anticline than in 
the Western one, yet are, in the main, sandstones with cal- 
careous layers below and sandy shales above. In both areas 
Dayia navicula is only found in the lower beds of Ludlow age, 
while Holopella characterises the upper ones. 
IV. [a). EXPOSURES BETWEEN CWM DOWLAIS 
AND CWM CAYO. 
These exposures are all in beds of Ludlow age. The 
Anticlinal arrangement so well seen to the South of Cwm 
Dowlais is absent in this more northerly tract, and the dips 
show that the beds have been much affected by pressure. 
On the hillside immediately to the North of the Wenlock 
Limestone in Cwm Dowlais recent excavations show a hard 
sandstone, which dips 16° N.N.E., but the beds soon bend, 
and at the top of the hill are dipping 35° W.S.W. The pub- 
lished I -inch map represents the Wenlock Limestone of Cwm 
Dowlais, as occurring in a dome with a quaquaversal di]y but 
this can now be proved not to be its arrangement. 
