144 
SILUEIA. 
[Chap. VII. 
Silurian rocks is seen to dip under the Old Eed Sandstone. At the eastern 
end of St. Bride's Bay, in Pembrokeshire, the Lower Silurian rocks, much 
dislocated, and associated with those bands of trap which form a striking 
outline in the Skomer Isles, plunge rapidly to the south-east, and sink 
under the strata of the mainland ; the latter consist chiefly of quartzose 
and schistose rocks, such as are well seen in Wooltack Pack, associated 
with much igneous matter. 
One of the highest of these broken bands (c), representing the Upper 
Llandovery rock, forms the foreground of Marloes Bay, — the chief cliffs 
in the landscape being composed of schists and sandstones of considerable 
dimensions, all highly inclined to the south-east, as expressed in the 
preceding vignette. The upper portion of these strata (d), comprising a 
few courses of impure limestone, contains the fossils of the Wenlock for- 
mation, and is covered by some equivalents of the Ludlow strata, in the 
condition of hard, siliceous, grey rocks, the whole being overlain in the 
distance by the Old Eed Sandstone (e) of Hook Point *. 
* In the corner of the accompanying Map, attention is directed to an enlarged portion of this tract, 
in which the powerful dislocations to which the strata have been subjected are marked. 
