88 SEVENTH REPORT—1837. 
On an Apparent Analogy between the New Red Sandstone of England 
and Ireland. By Captain Porttock. 
Capt. Portlock pointed out that he had first brought under the no- 
tice of geologists, at the Dublin Meeting of the Association, the occur- 
rence of fossil fishes in the new red sandstone of Tyrone. These he 
submitted to Professor Agassiz, who considered them a new species of 
the genus Paleoniscus, which he named Paleoniscus catopterus. As 
the genus Palzoniscus extends into the coal strata, Capt. Portlock 
wished to obtain some further evidence as to the true position of the 
sandstone containing these fossils. On excavating for this purpose all 
round the limited space in which the fishes had been found, he failed 
in meeting any more fishes, but he arrived on the same level in the 
quarry at thin red clay partings, exhibiting numerous impressions of a 
small bivalve shell, which both Mr. Strickland and Mr. Murchison on 
examination considered identical with the bivalve they had found ina 
portion of the new red sandstone of England, considered by them to 
belong to the keuper division of that great formation. This shell is 
the Posidonia minuta of Goldfuss, and is given by that author as a 
keuper fossil. According to Bronn, however, it is not confined to the 
keuper; and Capt. Portlock considers therefore the discovery of this 
shell in the Irish new red sandstone as valuable, inasmuch as it esta- 
blishes a general analogy between it and that of England, but he does 
not consider it sufficient alone to decide that the sandstone containing 
it belongs to the keuper. 
e 
On the leading features of the Geology of Ireland, and more particu- 
larly the situation and extent of the great Carboniferous or Mountain 
Limestone district, which occupies nearly two-thirds of the Island. 
By R. Grirritu, F.G.S., Se. 
In illustration of the succession of rocks which compose this extend- 
ed formation he brought forward a great section of the country, com- 
mencing on the sea coast below Benbulben, in the county of Sligo, and 
extending from thence nearly in an eastern direction to Butler’s Bridge, 
in the county of Cavan, a distance of 50 miles. This section, which 
exhibited in a very striking manner the profile of one of the most re- 
markable secondary districts in Ireland, and which crossed the sum- 
mits of Lacka, Lugnaquilla, Cuileceagh and Slieve Rushin Mountains, 
was laid down to a scale of 6 inches to a mile in length and 200 feet 
to an inch in height; the data for its construction, both for the heights 
and distances, having been taken from the Ordnance Survey. 
In describing this section, Mr. Griffith stated that the grauwacke 
slate of the county of Cavan was succeeded to the west of Butler’s 
Bridge by a series of strata, consisting of alternations of carboniferous 
limestone, yellowish grey sandstone and dark grey shale, amounting to 
a thickness of about 200 feet. These strata, to which Mr. Griffith gave 
the name of the yellow sandstone, rest unconformably on the grau- 
