182 
SILUEIA. 
[Chap. VIII. 
described by Portlock from Tyrone, or those of the fossil-bearing schists of 
Kildare, Wexford, and Waterford, are unquestionably Lower Silurian, and, 
for the most part, of the Caradoc age. Where, then, is the lowest Silurian 
in Connemara and other tracts in which metamorphic rocks appear beneath 
the fossiliferous strata ? My belief is, that the lower group is represented 
by the great underlying crystalline masses of the Bins of Connemara, and 
that the limestones included in those mica-schists are nothing more than 
the Lower Silurians altered, some of them being of the age of Llandeilo, 
and others the equivalents of the Caradoc rocks. Eecently the announce- 
ment of the existence of an Eozoon in the serpentinous green marble of 
Connemara seemed to lead to the opinion that these rocks were of Lauren- 
tian age. But even if it should be proved that the Poraminifer is present, 
its occurrence would in nowise affect my conclusion that the rock is Lower 
Silurian. The truth is, that, independently of the fact that the crystalline 
rocks of Connemara immediately underlie the Llandovery rocks, the suc- 
cession of quartz-rocks, limestones, and mica-schists is exactly similar to j 
that of the Highlands of Scotland, before described. Professor Harkness X 
has ably pointed out this analogy, and has shown that these Irish rocks 
are simply prolongations of the Scottish-Highland series. As already 
explained, the presence of an Eozoon (if that be admitted) has really little J 
bearing on the question ; for creatures of that low type of life may, as before 
said, well have lived on from the Laurentian to the Lower Silurian epoch. 
In the Galway tract we cannot, indeed, pursue a clear ascending order, 
any more than in Scotland, though it is possible that a succession like that 
of the district of Dingle may be detected. As yet it has only been observed 
that a coarse, chloritic, quartzose conglomerate overlies the fossiliferous 
beds in question — -a conglomerate which, according to Mr. Griffith, rises 
into mountainous masses on the north side of the Killery Bay. Alternating 
with green and purple slates and interstratified felspar-porphyries (t), these 
upper rocks, after an undulation, repose upon avast mass of greenish, grey, 
and reddish slate (c). The base of the fossiliferous series to the north of 
the Killery Harbour is composed of a dark and reddish-brown sandstone, 
under which is a conglomerate of mica-schist and other rocks, the whole , 
resting, as on the other side of the trough, on mica-schist (b). (See section, 
p. 180.) Then follows a boss of granite, * (Knock askeheen), which throws 
off crystalline schists on both flanks, — the masses in the north being 
bounded by the unconformable and horizontal Carboniferous Limestone of 
Clew Bay in Mayo. 
Seeing that we cannot there trace downwards fossils of higher antiquity 
than the middle portion of the Silurian series, it seems fair to infer that the 
subjacent quartz-rock, mica-schist, and stratified limestone of Connemara 
arc really the representatives of the Lower Silurian rocks. 
The progress of research will also, I trust, bring out other evidonces to 
I Quart. Journ. Geol. Soc. vol. xvii, p, 256. 
