j TRANSACTIONS OF THE SECTIONS. 43 
4 
green shales and gray sandstones, the shales containing the same fossils as before. 
These alternations are 300 feet thick, the limestone amounting to about one-third 
of the whole. Still ascending, there are a series of beds of arenaceous limestone, 
some of which are burned for lime, amounting to about 100 feet: from these beds 
108 species of fossils were collected, of which 96 are common to the upper members 
of the carboniferous limestone of Ireland. The most numerous are Product, Orthis, 
Atrypa, &c. These limestones are succeeded by beds of dark gray shale, gray and 
yellowish sandstone, and some thin beds of impure limestone about 360 feet thick ; 
the shales as usual containing fossils, the Modiola Macadami (Port.) being abundant, 
with some fish-scales and teeth, and plants. 
On the western shore of Killala Bay, the yellow sandstone of Kilcummin Head is 
succeeded by beds belonging to the carboniferous slate, or lower limestone shale, 
which are at once recognized by the absence of sandstone and the abundance of 
corals, particularly by several varieties of Fenestelle, which are very rare{in the shales 
beneath: these corals may be considered characteristic of the carboniferous slate. 
_ Thus it appears that on the north coast of Mayo there is a thickness of strata 
_ amounting to 1400 feet intervening between the bottom of the red sandstone and 
the carboniferous slate, the whole of which contains fossils, with the exception of 
the hard beds of red and gray sandstone, which with few exceptions are devoid of 
organic remains, whether at the base or top of the series. ‘The question then arises, 
can we separate the lower portion of the section, which assumes a red colour, from 
the upper, when it is remembered that the gray shales and limestones which alternate 
with the red sandstones contain more than three-fourths of the same fossils that 
are found higher up in the carboniferous limestone series? 
; Mr. Griffith next described the district situated to the north-east of Lough Erne, 
_ which contains a great variety of strata belonging to the Carboniferous, the Upper 
_ Silurian, and Mica-Slate systems. The succession of the strata as they occur in this 
interesting district was exhibited in two sections, one of which extended from the 
_ mica-slate district of the county of Donegal, north of Pettigoe, across the limestone 
and sandstone valley of Pettigoe, Kesh and Ederny ; it afterwards traverses the 
_ brownish-red conglomerate and sandstone district of Lisnarick and Irvinestown, and 
- in continuation the dark gray slate district of Lisbellaw, which contains Silurian 
fossils ; from whence it is continued across the limestone valley of Brookborough, 
_ thence over the Slievebeagh mountains, and terminates in the greywacke slate di- 
_ strict of the county of Monaghan, thus exhibiting the structure of the country fora 
length of forty-two miles. The other commenced in the mica-slate of Dooish 
mountain, county of Tyrone, and extended eastward, traversing the great district of 
brownish-red sandstone and conglomerate, and in continuation the carboniferous 
limestone series of the valley of Clogher ; then crossing the Slievebeagh mountains, 
terminates in the greywacke slate at Newbliss in the county of Monaghan. 
Commencing at the northern extremity of the most westerly of these sections, that 
near Pettigoe, we find the mica-slate covered in an unconformable position by a bed 
of red conglomerate about fifty feet in thickness, which is succeeded by yellow sand- 
stone alternating with dark gray shale, and occasional beds of dolomitic limestone ; 
_ the shale contains the casts of plants, and also in abundance Modiola Macadami ; 
_ these strata are about 150 feet in thickness: above we have alternations of dark gray 
hale with occasional beds of gray sandstone, and a few beds of calcareous clay iron- 
‘stone sixty feet thick. This mass of shale and sandstone is succeeded by a series of 
beds of blue limestone, occasionally alternating with dark gray shale and yellowish- 
 gtay sandstone 300 feet in thickness. It is remarkable that a thin bed of coal half 
an inch thick is included between two of the limestone beds at the base of this divi- 
ion: the limestone is frequently dolomitic, and, as is usual in such cases, fossils are 
frare occurrence. Above we havea succession of beds consisting of alternations of 
| limestone and dolomite about 100 feet in thickness, followed by alternations of dark 
gray impure limestone and black and gray shale 300 feet thick, on the top of which we 
have beds of gray siliceous limestone about sixty feet in thickness. These calcareous 
_ strata are succeeded by a great accumulation of beds consisting of gray sandstone and 
shale; in some places the sandstone, and in others the shale predominate, the whole 
deing interspersed with occasional beds of impure limestone, amounting altogether to 
a thickness of about 700 feet. The shale contains in abundance Modiola Macadami 
and the usual fossils belonging to the shale beds. 











































