Chap. VIII.] 
SILURIAN EOCKS IN DINGLE. 
179 
including a fine branched form of Heliolites, allied to H. inordinatus, 
Lonsdale. The curious Annelide-tube, Trachyderma squamosum, Phill., 
is found also in these beds and in a vertical position ; it is a species 
found in the Ludlow rock. 
The highest of the strata in which such fossils occur are purple-coloured 
and yellowish flag-like sandstones ; and these are seen to pass gradually and 
conformably upwards into the greenish and purple slaty beds forming the 
base of the great series termed ' Glengariff grits and schists,' which, not 
less than 7000 feet thick, occupy Mount Eagle and a long range of the 
Dingle coast. These beds are in their turn conformably surmounted by 
a thick suite of purple sandstones and conglomerates, containing pebbles 
and fossils derived from the underlying Silurian limestone. 
As, then, all these rocks distinctly overlie and pass upwards gradually from 
strata charged with Upper Silurian fossils, there can be no hesitation in con- 
sidering them to be the representatives of those slates and grits which, in 
Germany, Belgium, and North Devon, form the lowest portion of the De- 
vonian system. 
The preceding diagram, as prepared by Mr. Du Noyer, exhibits the gene- 
ral relations of the Silurian rocks of the Dingle promontory {a, b, c) to the great 
and superjacent masses of Old Eed Sandstone, whether they consist of the 
passage-beds (d), the ' Dingle ' and ' Glengariff grits ' (e), red sandstones 
and conglomerates (/), or the overlying Upper Old Eed Sandstone (h). 
These equivalents of the Devonian rocks will be commented upon in the 
next chapter. In the meantime it is enough to point out that the Upper 
Silurian and Ludlow fossils entirely terminate with the yellow-green and 
purplish sandstones (d), the latter being surmounted by rocks in which no 
organic remains have yet been discovered. 
In travelling along the west coast, or by the Carboniferous rocks of Clare, 
to the county of Galway, the geologist again meets with tracts which are re- 
plete with Silurian fossils. Lying to the north of the picturesque mountains 
known as the Bins of Connemara, these fossil bands, of rather older date 
than the Dingle Silurians, occupy the bold and precipitous sides of the deep 
Bay of Killery, and range over a considerable space eastwards, by Leenane, 
Maam, and Oughterard, to the shores of Loughs Corrib and Mask. 
Whilst on the eastern side of Ireland the eruption of the granite of 
the Wicklow Mountains has metamorphosed, as before said, the contiguous 
Lower Silurians, so in Connemara, on the west, we have a still more 
striking example of metamorphism, of a very large mass which, in my 
opinion, must be also considered Lower Silurian. The following diagram 
is reduced from one of Sir E. Griffith's coloured transverse sections across 
this remarkable district. After a personal survey of most of the Silurian 
tracts of Ireland, it has appeared to me best adapted to explain how cer- 
tain crystalline rocks, which from their mineral aspect have hitherto been 
supposed to be of higher antiquity, are (like the Highland rocks before 
n2 
