G. H. Kinahan — The Silurian Rocks of Ireland. 71 



this Old Red Sandstone is like the Yellow Sandstone of North Kerry, 

 but it is apparently much thinner ; while still farther east are the 

 already-mentioned rocks of Slieve Phelim. In Connaught, except in 

 Slieve Augkta, south-east Gal way, also in the north-west of Leinster, 

 the Old Red Sandstone is evidently a shore formation at different 

 horizons in the Limestones ; but in Fermanagh and Tyrone it seems 

 to be at the base of the Carboniferous. The rocks are more or less 

 similar to the Central Ireland type. 



We have now given a short resume of the Old Red Sandstone 

 adjuncts of the Carboniferous, and may now proceed to explain the 

 sections of the Silurian portion of the Old Red Sandstone. We have 

 mentioned that the Dingle Beds on the north of Dingle Bay, which 

 are capped unconformably by Carboniferous Old Red Sandstone, 

 are considered by such competent authorities as both Griffith and 

 Jukes to be the equivalents of the Glengariff Grits, which in the 

 Killarney district and in West Cork extend conformably upwards 

 into the Carboniferous rocks. The authority of these geologists is 

 scarcely to be questioned ; we therefore take it as proved, and 

 proceed to the next section. 



At Toormakeady, county Mayo, are conglomerates lithologically 

 somewhat similar to the Commeragh Old Red Conglomerates, but in 

 the beds at the base of the Toormakeady Conglomerates are Silurian 

 fossils; and further westward, in the very similar rocks of the 

 Mweelrea Mountains, Silurian fossils also occur. On these rocks the 

 Carboniferous strata lie unconformably. 



North of the Mweelrea rocks are the Louisburgh Beds. In them no 

 typical Silurian fossils have been found, but lithologically they are 

 similar, in part to the Mweelrea pebbly grits, and in part to the Salrock 

 slates ; the latter being the highest beds in the Galway Silurians. 



To the north of the Toormakeady Conglomerates, east and north- 

 east of Clew Bay, are the Croaghmoyle Conglomerates. No typical 

 fossil have been found in them, but lithologically they are similar 

 to the Toormakeady rocks, also to those to the north-east, in the 

 Curlew Mountains ; while they are capped unconformably by the 

 Cai'boniferous rocks. 



The Curlew Mountain rocks are lithologically more or less similar 

 to those already mentioned. They extend downwards conformably 

 into Silurians, having fossils similar to those in the Silurians that, 

 in the county Kerry, underlie the Dingle beds ; while upwards, 

 similar to the Kerry rocks, they are cut off and are capped uncon- 

 formably by the Carboniferous beds. 



The rocks of the Fintona district are lithologically similar to those 

 of the Curlew Mountains, and are also capped unconformably by the 

 Carboniferous series. Of these Portlock states that in one place they 

 seem to lie conformably on the Cambro-Silurians. Griffith, however, 

 in conversation, stated that he suspected there was a sequence of 

 rocks somewhat similar to that near Ballaghaderreen, and that 

 Silurian fossils occurred in them similar to those at Toormakeady. 

 This supposition rests solely upon information which I have not 

 had an opportunity of working out. 



