Royal Geological Society of Ireland. 87 



2. The Middle. — Consisting of a thin bed of Limestone lying 



between shales, with Carboniferous limestone genera and 

 species of shells, crinoids, and corals. 



3. The Loioer. — Consisting of massive reddish grits and con- 



glomerate with thin beds of shale. 



The author showed that the Carboniferous limestone of Ireland 

 undergoes in its extension northwards changes similar to those of 

 the same formation in Britain, when traced from Derbyshire into 

 Northumberland and Scotland. The calcareous member thins away and 

 is replaced by sedimentary strata of sandstone and shale, showing 

 approximately terrestrial conditions, productive of coal and ironstone. 

 It was thus that in the case of the Glasgow coal-field the limestone 

 of Derbyshire, several thousand feet in thickness, was represented 

 by only thin bands of earthy limestone, interstratified with a thick 

 series of grits, shales, etc., with ironstone and coal. In a similar 

 manner, the Ballycastle coal-field, with only a few feet of limestone 

 shown in the cliifs of the bay, was the representative of the Car- 

 boniferous limestone of the centre of Ireland, nearly 3,000 feet in 

 thickness. 



Mr. Hull regarded the Lower division (No. 3) of the Ballycastle 

 beds (as above described) as undoubtedly the representative of the 

 " Calciferous Sandstone Series " of the Geological Survey which lies 

 at the base of the Carboniferous rocks of the West of Scotland, and 

 that the Middle and Upper divisions (Nos. 2 and 1) correspond to 

 the Carboniferous limestone series, or lower coal-field of that 

 country. 



As regards the palasontological evidence, it was in favour of this 

 view, as far as it had been studied. Out of 33 species observed in 

 the limestone band of Ballycastle Bay, 50 per cent, had been de- 

 scribed in the Lower Carboniferous rocks of the West of Scotland,^ 

 and one of the uppermost seams of coal lying above the limestone had 

 yielded Lingula squamiformis, a form characteristic of the limestone 

 series in the North of England, as also in Scotland and Ireland. 

 Mr. W. H. Baily, F.G.S., concurred in the view of the age of these 

 beds, on palseontological grounds. 



The author concluded by pointing out several features of similarity 

 between the Ballycastle beds and the Lower Coal series of the West 

 of Scotland, such as the occurrence of several beds of " Black -band" 

 ironstone ; the hydraulic and earthy character of the limestone of 

 Ballycastle Bay exactly resembling the "Arden" and"Cowglen" 

 bands of Glasgow. Some uncertainty still remained whether there 

 were any beds in the Ballycastle district as high in the geological 

 series as the Millstone grit, or true Coal-measures ; but until more 

 light could be brought to bear on this question by further ex- 

 ploration, and a complete investigation by the Government Sur- 

 veyors, the author meanwhile regarded the whole series as Lower 

 Carboniferous. 



^ Trans, Geol. Soc. of Glaso-ow. 



