1848.] RAMSAY AND AVELINE ON THE STRUCTURE OF WALES. 297 
» The rocks which may be called the igneous series, with the under- 
lying rocks of Barmouth and the Longmynd, were evidently disturbed 
before the deposition of the Caradoc sandstone. In some places we 
have direct evidence of the margin of the Caradoc sea, as at the Long- 
mynds. Throughout most of the range described, if its lithological 
character be examined, it will be found to be composed in great part 
of trappy felspathic debris, and it seems not unlikely that (as we 
certainly know part of the Bishop’s Castle country was above water 
before the deposition of the Caradoc) the igneous countries of Merio- 
neth, Bishop’s Castle and Builth also rose above the water, and by the 
waste of these old lands the Caradoc sandstone was in part formed. 
That the Wenlock shale rests more or less unconformably on the 
Caradoc can be proved by the fact that it overlaps the Caradoc near 
Bishop’s Castle, gradually creeps over it towards Builth, and in that 
country rests directly on the lower part of the igneous series on the 
one side and on the higher part on the other (see list of fossils). 
The sandstones to which we have so often alluded as underlying the 
Caradoc can be followed in their strike towards the small boss of ashy 
traps at Baxter’s Bank, where they are about 1800 feet above the traps. 
From thence they can be traced to Garth, six miles west of Builth, 
where in their turn they are overlapped by the Wenlock shale, again 
to appear at Castell-craig-gwyddon near Llandovery. South of 
Rhayader they roll over to the west, rise again on the left bank of 
the Teifi greatly increased in thickness, and roll over again on the 
right bank, from whence in a series of contortions they reach the sea 
at Aberystwyth. 
When we consider this unconformity in connection with the old 
coast line of the Longmynds and Bishop’s Castle igneous series, there 
seems little doubt that both at Builth and Bishop’s Castle these lands 
were above water before the deposition of the higher rocks, and gra- 
dually became depressed during the accumulation of the Wenlock and 
Ludlow rocks, and thus we can show that rocks once at the surface as 
land, during a period of lengthened depression had many thousands 
of feet of marine strata deposited above them, and now are again 
by denudation exposed at the surface. 
Memorandum respecting some Fossiliferous Localities alluded to in 
Professor Ramsay and Mr. AvELINE’s Paper, as noted on the 
spot, by Professor Epwarp Forses. 
1. Between Church Stretton and Bishop’s Castle the Caradoc 
sandstone rests directly and unconformably on the Longmynd rock, 
which was consolidated at the time of the deposition of the Caradoc, 
since pebbles of it occur in the latter: hollows in it are filled with 
Caradoc. The fossils in the Caradoc here are Terebratula furcata 
and decemplicata, Pentamerus levis, and a Cybele. On the sand- 
stone rests a limestone full of the Pentamerus, associated with shales 
full of Orthis elegantula. The characters of these beds, mineralogi- 
cally and palzeontologically, indicate their identity with the band of 
““Woolhope”’ limestone, seen in sequence with the Caradoc and Wen- 
