140 
JOURNAL OF THE GEOLOGICAL SOCIETY OF DUBLIN. 
The first member of the system, the yellow sandstone of Dura 
Denn, is the equivalent of the Irish Old Red, or, at least, of the 
upper part of it. It appears to me that this ought not to be sepa¬ 
rated from the Carboniferous formation; the three subdivisions of 
which, as already enumerated, from the general parallelism of their 
beds, were undoubtedly deposited in one geological era, and a com¬ 
paratively calm one it was. Abundant proofs exist of tremendous 
disturbances previously in the upturned edges of all the lower rocks, 
and subsequently in the contortions of the strata of the formation 
itself, where they are not broken up by faults; for, even in those 
contortions, the beds of sandstone, limestone, shale, and coal, are 
alway parallel to each other through every undulation and inclina¬ 
tion. Besides this, certain fossils are common to the whole three 
subdivisions. I saw in Professor Haughton’s cabinet, in Trinity 
College, some specimens procured from the yellow sandstone, or 
upper part of the Old Red, at Porter’s-gate, near Hook Head, in 
Wexford. Among them were Orthis crenistria , Atrypa pleurodon, 
Producta caperata , Producta concinna, Producta setosa , Sangninolites 
sulcatus , Lithodomus dactyloides , and others, all mountain limestone 
fossils. Again, in the county of Tyrone, in the river near Cooks- 
town, and about twenty chains below Kildress Bridge, specimens 
were obtained by Colonel Portlock, from Red Sandstone. The bed 
which contains them is near the base of the Old Red in that locality. 
Those specimens are in the collection of the Geological Survey, in 
the^Museum of Irish Industry, Stephen’s-green. They are very 
fossiliferous; and among them are found Producta Martini , Producta 
setosa , Orthis umbraculum , Orthis crenistria , Atrypa pleurodon , and 
others; all common in the mountain limestone. 
Neither are the coal rocks without similar fossils. At Carrow- 
nanalt, two miles N. E. of Keadue, I found in a ravine in the coal- 
measures thirty-five species of shells and Trilobites, in a few blackish 
calcareous beds, altogether about three feet thick. This fossili¬ 
ferous band is about 200 feet over a bed of coal, which has been 
worked in the vicinity. Of the thirty-five species, twenty-six 
occur in the mountain limestone, and are, therefore, common to 
both. 
This double link, the parallelism of the beds, and the commu¬ 
nity of the fossils, is against the Old Red being separated from the 
Carboniferous rocks, and joined to other inferior rocks, with which, 
in Ireland at least, they have no relation but contact. 
