288 
2.—Section from near Treffgarn Bridge to the north of Ford Bridge on the Road from Haverfordwest to Fishguard. 
(Scale, 6 inches to 1 mile.) 
Fig. 
H. HICKS ON A NEW GROUP OF 
Treffgarn 
Rock 
- <A 
SSN ‘ 
SNEAKY 
RON \ 
CORA 
x 
I) 
AW 
b 
WEN 
UMW 
WS 
WN 
\S 
Silurian, 
Silurian. 
Cambrian. 
Chloritic schists, breccias, &c. 
Pebidian. 
a 
a 
Arvonian, 
a, a. Hilleflintas. 
6. Breccias and slates. 
to the road-side, and offer very 
favourable opportunities for their 
examination and for the collection 
of specimens. 
Another area of these rocks oc- 
curs to the N.W. of those just de- 
scribed, here also running in a di- 
rection from N.E. to §8.W., and 
parallel to and apparently flanking 
towards the $.E. the Dimetian 
axis of Brawdy and Hayscastle. 
The detached mass on the coast, 
in a line with this ridge, is also 
more of the nature of these rocks 
than of the Pebidian or Dimetian. 
It will be seen also that they 
form a considerable proportion of 
the so-called Dimetian axis at St. 
David's. 
In my last paper on the Dime- 
tian and Pebidian rocks of St. 
Dayid’s*, I called attention to the 
fact that the series 1 and 2 in the 
general section there described 
were lithologically very unlke 
the series 4, 5, 6, and 7, which 
I stated formed the bulk and ty- 
pical portions of the Dimetian. 
The series 1 and 2 were called 
generally quartz-porphyries and 
quartz-felsites, and were then sup- 
posed to have either a volcanic or 
intrusive origin. ‘They were also 
excluded in the calculation of the 
thickness of the Dimetian on ac- 
count of their doubtful character 
and dissimilarity to the rocks of 
that group. But as at that time 
there was no evidence to show that 
these were distinct from the Di- 
metian in any other way than in 
their mode of origin, and as, more- 
over, it was clearly seen they could 
not be allied to the Pebidian (since 
the latter everywhere rested upon 
them unconformably), I felt justi- 
fied in keeping them with the Di- 
metian. 
* Quart. Journ, Geol. Soc. yol, xxxiy. 
p. 153, 
