Notices of Memoirs—Dr. Hicks—Cambrian in Wales. 549 
they are, though not actually at the base, yet very near the base of 
the Cambrian rocks of that area. The most important conglomerates, 
however, in this district are those which were discovered by Pro- 
fessor Hughes and the author on the east side of the Trawsfynydd 
Road, between Cae Cochion and Penmaen. Here the conglomerates 
rest unconformably upon an older series of rocks, and large fragments 
of the latter occur plentifully in the conglomerates. 
ANGLESEY. 
As Sir A. Geikie has recently admitted that many of the rocks 
in Anglesey, coloured on the Geological Survey Map of that island 
as ‘‘altered Cambrian (and partly Silurian),” are “undoubtedly far 
older than at least any of the Cambrian rocks of Anglesey or 
Caernarvonshire,” the evidence furnished by the basal beds where 
they rest on these rocks is highly important. The author was the first 
to point out, in a paper read before the British Association in 1879, 
that the patch near the centre of Anglesey coloured as “intrusive 
granite chiefly of Lower Silurian age”’ contained within its boundary 
rocks of pre-Cambrian age, evidently the oldest rocks in the island. 
(The rocks in this patch Sir A. Geikie now says appear to him to be 
“unquestionably Archean.”) In the year 1884 the author further 
showed that the Cambrian conglomerates near Llanfaelog contained 
large pebbles of granitoid and other rocks, which, on microscopical 
examination, proved to be identical with rocks in situ in their 
immediate neighbourhood. 
Professor Hughes has shown by fossil evidence that the beds 
which overlie the conglomerates near Llanerchymedd are of Upper 
Cambrian age, and, as these are separated by faults from the con- 
glomerates and grits, it is clearly justifiable to classify these beds 
as the basal beds of the Cambrian in that area. The basal Cambrian 
beds near Beaumaris furnish equally convincing proofs of proximity 
to a shore-line composed of pre-Cambrian schists and felsitic rocks. 
CAERNARVONSHIRE. 
Bangor and Caernarvon.—The basal beds at and near Caernarvon 
described by Professor Hughes show clearly that they must have 
been deposited along a shore-line where granitoid and felsitic rocks 
were undergoing denudation, and the absence there of the usual 
thickness of overlying Cambrian rocks is due, the author believes, 
mainly to faults, but in part also to the unevenness of the pre- 
Cambrian land-surface. There is much evidence in the various 
areas to show that the pre-Cambrian land-surface was very uneven 
in character, and that the Cambrian sediments were accumulated 
along fairly well-defined lines of depression. 
Bethesda, Llyn Padarn, and Moel Tryfaen.—The basal beds of the 
Cambrian in these areas, where not removed by faults, are also 
conglomerates, and the fragments in the conglomerates are mainly 
such as would be derived by denudation from the ridge of rocks 
in the neighbourhood which had been claimed by the author and 
Professor Hughes as of pre-Cambrian age. These views, put forward 
