ROCKS OF PEMBROKESHIRE, 543 
reality they are the rocks which form the cliffs for a considerable 
distance along the east shores of that harbour. This same strange 
mistake is evident also in his section, as a most abnormal thickness 
is given to the sandstones above the conglomerates, to enable the 
other beds to get into position. It certainly is a curious fact that 
the greatest exposure of Cambrian conglomerates in the neighbour- 
hood of St. David’s should be thus missed, as it evidently must have 
been, by the Director-General. This error of his furnishes the best 
proof that could be desired of the great unconformity between the 
Cambrian conglomerates and the Pebidian; for had the former con- 
tinued to lic on the same beds of the latter as at Rhosson, less than 
a mile to the south, where they are well exposed, their position 
would be a quarter of a mile to the east of Porth-seli, as shown in Dr. 
Geikie’s map. The facts, however, as stated above, prove that in this 
mile of country a quarter of a mile in thickness of nearly vertical Pebi- 
dian strata has been overlapped by the conglomerates. The sketch, 
fig. 15, shows the Cambrian conglcmerates reposing upon the Pebidian 
Fig. 15.—Sketch of Cliffs on south side of Ogof-golchfa, Whitesand 
Bay, showing basal Cambrian Conglomerate (1) resting uncon- 
formably on Pebidian rocks (series ¢). 
Index as in Map, Pl. XXTV. 
beds at Ogof-golchfa, Whitesand Bay. The conglomerates are of very 
great thickness here, the pebbles of large size, and many of the frag- 
ments are such as could only be derived from the Pebidian beds 
below. The large pebble exhibited by me at the meeting, when the 
second part of Prof. Geikie’s paper was read, which was claimed by 
Mr. Peach to be a segregation, came from these beds; and Note 69 
will show that it is a large pebble of a schistose quartz-felsite 
identical with the quartz-felsites of series ¢ of the Pebidian. The 
conglomerates at Ogof-golchfa repose upon schistose felsitic tuffs 
and breccias, and some schistose argillites. Notes 39 and 40 refer 
to some of these rocks. 
Section, fig. 1 (p. 524), runs in a S.E. direction from the south 
side of Porth-seli across the Pebidian rocks and the Dimetian 
axis to the shore of St. Bride’s Bay below Nun’s Chapel. It 
shows the usual series of Cambrian rocks in this area, and the 
Pebidian series as in the section to the south, but with a greater 
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