Vol. 70.] ORDOVICIAN AND SILURIAN OF LOUGH NAFOOEY. 109 



200 yards west-south-west of the hamlet. The last two exposures, 

 however, are now overgrown, and the breceia is no longer visible. 

 At all these localities the limestone-breccias appear to be vertical. 



III. The Mweelrea Grits and Conglomerates 

 (Llandeilo). 



These grits and conglomerates, which bound the Kilbride area on 

 the north-west, were not described in our paper on that area, while 

 in our earlier papers on the G-lensaul and Tourmakeady districts 

 they are referred to as of (?) Bala age. 



As shown in our map (PI. XVII), they form a band about 300 

 yards wide, extending along the southern shore of Lough Nafooey, 

 where they consist of coarse quartzose grit passing in places into 

 tine breccia or conglomerate. They dip at a high angle north- 

 wards, and, although their actual junction with the Arenig rocks 

 is- nowhere visible, there can be little doubt that it is a simple 

 unconformity. Along part of their outcrop, about a mile east of 

 Curraghrevagh hamlet, pale flaggy beds accompanied by grey 

 •cherty bands occur at their base. About 1200 feet up in the 

 Mweelrea Grits a band of very coarse conglomerate, with blocks of 

 granite and schist, is seen. This is well exposed on the hillside 

 north-west of Curraghrevagh hamlet. 



The coarse grits, displaced by a fault, are also seen underlying 

 the- Silurian beds half a mile north-west of Benbeg. A band of 

 pale-yellow felsite, exactly like the band in contact with their base 

 at Curraghrevagh, follows their southern outcrop here. 



IV. The Silurian Rocks. 



The Silurian rocks extend westwards from the Finny River with 

 a uniform west-south-westerly strike, until a point south-west of 

 Bencorragh is reached (2£ miles). The southerly or south- 

 easterly dip is always high, 60° to 80° in the neighbourhood of 

 Drin ; while south-east of Bencorragh the rocks are often vertical, 

 or even slightly overfolded. South-west of Bencorragh they are 

 broken through by one important, and by two minor, cross-faults, 

 which shift their outcrop some 500 yards northwards. They then 

 strike nearly due east and west for about If miles, until, at a 

 point north of the top of Benbeg, they are faulted again to the 

 south, and their strike once more swings round to the west-south- 

 west. 



In the eastern part of the area the Silurian rocks form the 

 top of the ridge ; but their strike is such that they cross the ridge 

 about half a mile east of Bencorragh, which, together with all the 

 high ground for some distance eastwards and westwards, is formed 

 of spilitic lavas. West of the fault, which shifts their outcrop to 

 the north, the Silurian rocks again form the top of the ridge; and, 

 as they are finely exposed, and are tilted up until they are vertical 

 or dip at angles of 80° or more southwards, it is easy to ascertain 

 the thickness of the various bands. 



