Vol. 70.] ORDOYICIAX AXD SILURIAN OF LOUGH NAPOOEY. Ill 



bostonite intrusion. The pebbles of the conglomerate are chiefly of 

 pink quartzite, with some of felsite and, it is interesting to note, of 

 a rock closely resembling the adjacent bostonite. The conglomerate 

 is shown in our map (PL XVII) only where it was actually ob- 

 served ; it probably has a wider extension, but is concealed by peat. 



(2) The Red Sandstone. — This is identical in lithological 

 character with the Red Sandstone of Kilbride, which it resembles 

 also in having yielded no fossils. To the south-west of Bencorragh,. 

 on the hillside and in the stream-bed, it contains a thin band or 

 bands of purple sandy shale, similar to that forming Band 5 a of 

 the above table. Some 15 feet of this shale, passing up into flaggy 

 beds, are seen in a stream- section a quarter of a mile west-south- 

 west of the top of Curraghrevagh. 



The lithological resemblance between this red sandstone and 

 shale and the Salrock Beds of Ludlow age in the Leenane area is 

 probably the reason why the former were coloured as Ludlow Beds 

 in the Geological Survey maps. 



(3) The Annelid Grits. — These rocks are well exposed near 

 Drin, and for some distance along the ridge to the west the peculiar 

 worm-tubes which they contain are much in evidence. Farther 

 west the worm-tubes are not seen, none having been noticed to 

 the west of Bencorragh. In the western part of the outcrop the 

 Annelid Grits thin considerably, become more thinly-bedded and 

 flaggy in character, and include a marked development of quartz- 

 conglomerate : this does not form a continuous band, but occurs 

 in patches. In the stream running southwards from the col west 

 of Bencorragh, these grits are about 90 feet thick. 



(4) The Finny School Beds (Calcareous Flags). — These 

 beds, which reach a thickness of some 820 feet on Curraghrevagh,. 

 are of exactly the same character as those at Kilbride, and are 

 very fossiliferous in places, especially at Drin. Like most of the 

 Silurian deposits the Finny School Beds decrease in thickness when 

 followed westwards. A list of the fossils found in these beds at 

 Kilbride appears on p. 86 of our former paper. We found no 

 additional species in the Lough Nafooey area. 



(5«) The Purple Sandy Shales (Tarannon). — These 

 form a well-marked band traceable throughout the whole Lough 

 Nafooey area, and seem to maintain everywhere much the same 

 thickness — about 80 feet, as in the Kilbride area. 



(5b) The Grey-Green Flags (Tarannon). — South-west 

 of the top of Curraghrevagh pale-grey or green flaggy beds, 

 reaching a thickness of 225 feet, are seen between the Purple Sandy 

 Shales and the Doon Rock Grits. They yielded there Monograytus 

 priodon Bronn and M. galacnsis Lapw., kindly identified by 

 Miss G. L. Elles, D.Sc, who remarks that the M. priodon is 

 not the stiff, wide Wenlock form, and that the occurrence of 

 M. qalaensis is in accord with the field-evidence as to the probable 



