722 
Proceedings of the Royal Irish Academy. 
allied rock. Possibly this may be correct ; but if so, there have been 
very complicated changes, as the original eruptive sheets first became 
dolomites and dolomitic limestones, prior to changing into the " Gon- 
nemara serpentines." This last change can be ocularly proved in 
different places, but especially in the Lisoughter marble quarries. 
The tracts and courses of diorite and hornblende rock associated 
with the limestone of the Clifden and Oughterard valley, but more 
largely developed in the schist of the country to the southward, are 
stated to be the untorn-up portions of the igneous rocks that originally 
occupied the entire area ; they having escaped the shearing and 
attenuating that tore up and i^econstructed the associated rocks. The 
improbability, if not the impossibility, of such a change, has already 
been considered {^ante, p. 710). 
The rocks of the Bennabeola and adjoining ranges were considered 
by me (as stated in previous publications) to be the oldest rocks in the 
region. The recent researches of the American geologists in the 
metamorphic rocks of the Lake Superior district have, however, illus- 
trated how easy, in metamorphosed and disturbed regions, unconfor- 
mabilities may be passed over ; and how masses of strata, belonging to 
quite distinct periods of time, may be classed together as portions of 
one series. 
It is therefore quite possible that my determination as to the clas- 
sification and age of the Connemara rocks may be incorrect, as under 
the Silurian basin of Killery Eay there may be an unconformability, 
the rocks to the northward being younger than those to the south- 
ward;^ also the Conga lake conglomerate may also indicate a second 
unconformability, now not very conspicuous on account of the evident 
inverted folding. The Conga Lough conglomerate may, however, pos- 
sibly be, as I formerly supposed, the equivalent of the pebbly quartzite 
north of Errilf, county Mayo. 
ISTevertheless, there are still reasons for supposing that ray original 
classification may possibly still be correct. Because, as shown in the 
original Paper, read before the Academy, if we take the rocks of the 
Bennabeola, as the lowest in the sequence, and go northward to Clew 
Bay, county Mayo, eastward to Loughs Mask and Corrib, and south- 
^ The black graptolitic shales of the Owenbrin valley are lemarkable, nothing 
like them being found in the adjoining portion of Co. Mayo. The black schists, 
however, immediately in the neighbourhood of Galway town, and the black horn- 
stone of Gorumna Island, north of Galway Bay, are, however, rocks that originally 
might have been black graptolitic shales. 
