186 Reports and Proceedings—Geological Society of London. 
of mixed agglomerate, and terminated masses of limestone and 
quartzite filled with brecciated fragments. 
5. The Northern District.—This commences in the south with the 
chloritic schists, but soon becomes slaty, and such rocks with grits 
occupy the greater part of the area. But towards the north we 
reach the volcanic facies, characterized as usual by ashes, ag- 
glomerates, quartz knobs, in one place near Bull Bay, seen to cross 
the bedding, and sporadic limestones at Llanbadrig, showing oolite 
within oolite, and suggesting its origin by a petrifying spring. 
Above the quartz is found a great conglomerate, apparently derived 
from it, and immediately above this conglomerate occur the fossils 
discovered by Prof. Hughes, and no line of separation can be dis- 
covered between them and the rest of the rocks in the district. 
These fossils have been referred to Bala species, and there are 
three alternatives to choose: either (1) they are not Bala fossils, 
but are characteristic of the Pre-Cambrian rocks; or (2) they are 
Bala fossils, and the dividing line has as yet been missed; or (3) 
there is no dividing line, and the whole series is of Bala age. 
Against the latter is their similarity to the rocks of the eastern 
district definitely overlain by Cambrian; and against both the two 
latter is the fact that the series is unconformably overlain in the 
neighbourhood by other conglomerates succeeded by black shales in 
which Llandeilo Graptolites have been recorded. 
6. The District north-east of Parys mountain is a volcanic complex, 
in which granite and felsitic rocks with others of a more basic 
character are inextricably mixed with the débris of the same 
materials, and both are altered so as to be, in most places, in- 
separable. This is connected on the N.W. side with grey gneiss. 
In the Lleyn the rocks belong to the volcanic facies, in which 
great masses of quartz-felsite, foliated at the edges, are intruded. 
Here also are found the quartz knobs and sporadic limestones as 
well as diabase-flows. At Mynydd ystum is found an isolated patch 
of grey gneiss. 
The area between Bangor and Caernarvon has lately been shown 
to contain some felsite-flows, and also granites, apparently intrusive 
into ashes, which may belong to the volcanic facies. 
At Howth, near Dublin, the rocks have all the characters of the 
South-Stack series, to which they may be correlated; and these are 
followed upwards by the well-known Bray-Head rocks, which differ 
from them in character, but whose fossils are not of Cambrian species. 
The succession thus shown in the various districts consists of the 
following in ascending order. The grey gneiss, becoming more 
quartzose, micaceous, or chloritic in parts, and so representing the 
quartzite and the chloritic schists of other districts; changing through 
chloritoid schists into two facies, viz. (1) the slaty, represented best 
in the northern district, and also as the South-Stack series; and (2) 
the volcanic facies. No further deposits are recognized in the areas 
of the volcanic facies, but i in the slaty area of Howth the Bray-Head 
rocks succeed. 
To the whole system of rocks the name of Monran is applied, as 
