Chap. VIII.] 
SILURIAN ROCKS, GALWAY. 
181 
conglomerate, sandstone, and schists, c, containing fossils, as at Let- 
tershanbally, Blackwater Bridge, Leenane, Maam, and other places. 
Now these remains, all unequivocally Silurian, belong by no means to 
the lowest members of the system. On the contrary, though some of them 
are found elsewhere in the Lower Silurian strata, their prevalent species 
refer the beds rather to the Llandovery or intermediate rocks. In fact 
the strata resemble, both zoologically and lithologically, some of the upper 
fossiliferous greywacke before described on the banks of the Girvan Water, 
in Ayrshire; many of the same species occurring in the two districts. 
Several of the Irish fossils are, indeed, more common in the Upper Silu- 
rian, both of England and Wales. 
Some of the remains in the beds near Maam would be considered Lower, 
and others Upper Silurian, there being among the latter Bellerophon 
trilobatus, first published from the Tilestones or summit of the Lud- 
low rocks. "With the widely spread fossils Strophomena depressa and 
Atrypa reticularis, which occur in nearly all the Silurian strata, we here 
met with Pentamerus oblongus, Orthis calligramma (virgata), 0. reversa, 
Atrypa hemisphserica, &c, which elsewhere are known only in rocks of 
Llandovery age, associated with Rhynchonella Wilsoni and Retzia cuneata, 
Bellerophon trilobatus, and some Lamellibranchiata, such as the Pte- 
rinea retroflexa and Cucullella antiqua, which were long ago described 
as true Upper Silurian fossils. Here, also, in the beds of junction 
with the mica-slates, are the Chambered Shells Cyrtoceras approxima- 
tum, Orthoceras bullatum, 0. ibex and 0. angulatum, — species formerly 
supposed to mark the Upper Silurian only, but since found also in some of 
the lower strata. Among the Trilobites we have even our persistent friend 
Calymene Blumenbachii, that ranges from Snowdon to Ludlow, and Encri- 
nurus (Amphion) punctatus, together with the genus Stygina, only yet 
known in Lower Silurian strata, and apparently the same species which is 
found in Tyrone, and Cyphaspis megalops, a Dudley fossil. Again, the 
Corals from another locality (Kilbride) present us with such species as 
Eavosites cristatus, E. Gotlandicns, E. multiporatus, &c, which are usually 
Upper Silurian types *. 
To sum up, then, we have seen inDingle a copious and unmistakeable series 
of true Upper Silurian rocks and fossils, surmounted by Lower Devonian 
schists, slates, grits, and sandstones. In Connemara and the adjacent tracts, 
and thence extending to Uggool in Mayo, the intermediate group of Llan- 
dovery rocks is strikingly apparent, though in fragments and patches only • 
whilst a multitude of organic remains, whether they be the well-defined forms 
ordinate to the upper portion of the mica-schist, are many other such junctions (as around Maam) 
which, as in Argyleshire on both sides of Loch where the relations are quite discordant. 
Fyne, exhibits many of the appearances of ordi- * This enumeration of fossils was given in the 
nary stratified limestone, in respect to bedding, previous edition. Since then Prof. Harkness has 
joints, and way-boards ; but we could detect no gone over the same ground, and his observations 
fossils in it. The above section exhibits the confirm my conclusions. (See Quart. Journ. G-eol. 
strata, c, containing Silurian fossils, reposing un- Soc. vol. xxii. p. 512.) 
conformably on these micaceous rocks ; and there 
