ROCKS OF PEMBROKESHIRE. 545 
are other schistose felsitic rocks, and some rather dense-looking 
schistose beds (No.41)*. To the N.E. at Maendewi, Rhodiad, and 
Gwrid, beds belonging to series b and ¢ are exposed, and the rocks 
here are described in Notes 25-27. The series d and ¢ found near 
Ramsey Sound and Porth-seli are not well exposed to the north of 
Croeswdig rocks. Indeed over the burrows and on the moors which 
occur to the N.K. there are scarcely any exposures at all, but the 
few that have been seen show that rocks belonging to series d, at 
least, occur here. North-east of Trelethydfawr Cambrian rocks are 
thrown down against lower members of the Pebidian by faults ; and 
near Treliwyd some few beds of the Cambrian cong'omerates are 
seen. 
So far as it has been possible, the whole of the St. David’s area 
has been explored. In the above remarks the general facts ob- 
served are given; and I do not think it is possible for other evi- 
dence to appear which can in any important degree vitiate the main 
conclusions arrived at. 
8. Ramsey Island. 
In my former paper I mentioned the occurrence in Ramsey Island 
of quartz-felsites, breccias, and killeflintas belonging to the Arvo- 
nian series, and that these were covered at one point unconformably 
by Cambrian conglomerates, mainly built up from fragments derived 
from the former. In the spring of last year I revisited Ramsey 
Island with Prof. Hughes and party, and we were able not only to 
confirm our previous conclusions, but to add somewhat to the evi- 
dence. The interpretation is given generally on the Map, Pl. XXIV. 
We found that the mountainous area called Carn consists in part of 
old rhyolites, of beds of fine ash (hilleflintas), and of rough breccias 
(Notes 12-14). Note 15 refers to one of the detached masses whose 
age is not clear at present, but the probability is that they are Pre- 
Cambrian. The Cambrian conglomerates here are almost entirely 
made up of very well rolled fragments of the rocks found under- 
lying them. They attain to a considerable thickness, especially 
towards the N.W., and appear to be succeeded by some of the 
greenish sandstones. The main part of the Cambrian, however, has 
been dropped by fanlts, as the Arenig rocks are exposed within a 
short distance of the conglomerates on the coast. That some, at 
least, of the intermediate beds must have been deposited in this 
area is clear from the fact that beds belonging to the Lingula Flags 
and to the Tremadoc series occur at the north end of the island, 
underlying the Arenig rocks +. 
* Prof. Blake’s map, Quart. Journ. Geol. Soc. vol. xl. p. 295, is incorrect in 
showing Cambrian rocks in this immediate area. 
+t In a recent letter Prof. Bonney, who has so frequently assisted me in 
these inquiries, writes to me as follows :-—“‘ As you are aware, I have examined 
some parts of the St. David’s district pretty carefully, and feel bound to tell 
you that though I have had a rather large experience in studying the junctions 
of igneous and sedimentary rocks, I saw nothing at Porth-clais or at Ogof- 
Nesugn which led me to suspect that the ‘Dimetian’ was intrusive in the 
