Kinahan — On Irish Arenaceous Rocks. 521 



accumulations, while south-east of the trough there are none, ex- 

 cept a few thin subordinate sandstones. West of the Leinster 

 range, coming up from the south, these shore-rocks gradually thin 

 out, and disappear south of Bagnelstown, not to be met further 

 north except in small patches, such as at Newcastle, south-east of 

 Celbridge (Kildare), where, we may suppose, there was a cape, 

 alongside which a beach accumulated. In connexion with the 

 Chair of Kildare, and the other small exposures of Ordovicians, 

 that seem to have been islands in the Carboniferous sea, these 

 shore-beds only occur at one side of the older rocks. Margining 

 the large protrusions of Ordovicians in the central plain of Ire- 

 land, the Lower Carbonifereus Sandstones are very continuous, 

 while in the west of the Co. Galway, margining the older rocks, 

 they are only found at Oughterard and Cong, in places that must 

 have been bays. In western Mayo they are very continuous ; 

 but in the rest of that county, in Sligo and Roscommon, they, 

 in general, only occur to the south or south-east of what was 

 the old land : the exceptions being the tracts north-west of the 

 western end of the Curlew Mountains {north-east Mayo), and those 

 north-west of the Ox Mountains [Co. Sligo). In the large south- 

 west and north-east bay, between the Ordovician land, south and 

 south-west of Lough Neagh, and the Silurian land, between 

 Loughs Neagh and Erne, the Lower Carboniferous Sandstone, ex- 

 cept in the north-east portion, was very continuous ; but to the 

 north of Lough Erne the Carboniferous Limestones, like as at 

 Oughterard, were accumulated against an old cliff, sandstones only 

 being deposited to the north-east, in the Termon River valley. In 

 the tracts of Carboniferous to the northward [Donegal, Londonderry, 

 and Tyrone), the shore-beds nearly invariably only occur to the 

 north, as in the tracts at Donegal Bay, and westward of Omagh. 

 At Feeny, however, westward of Dungiven, there is a small tract 

 that seems to have accumulated in a small bight, or bay, where the 

 shore-beds were to the southward ; while in Fanad, west of Lough 

 Swilly, is the small tract to which attention has lately been di- 

 rected by Messrs. Hull and Cruise, in which the conglomeritio 

 accumulations, as pointed out in a paper by Mr. Mahony, occur 

 along the southern shore, and silts occur along the northern. 



[In the Lower Carboniferous Sandstones, and also in the subsequent ' ' shore accu- 

 mulations," there are two distinct types, the lowest beds and those on higher horizons 



