Yol. 52.] ON THE KILDARE INLIER. 595 



IV. Dunmurry and Grange Clare Hills. 



These two hills occur to the south-west of the Chair and Grange 

 Hill, and are cut off from them by a fault which runs along the 

 Talley traversed by the Kildare and Rathangan road. The rocks 

 which form these two hills are, as a whole, strikingly different from 

 those forming the hills to the eastward. 



The lowest beds found in this part of the inlier crop out along 

 the northern and north-eastern face of Dunmurry Hill. They con- 

 sist of somewhat black shales, highly ochreous in places, which pass 

 up into more olive-green shales, and are succeeded by a band of red 

 earthy shales. These red beds are very easily marked, and some- 

 times where they are not seen in situ their presence may be inferred 

 from the colour of the soil. They are also seen in the road ^ mile 

 north of Dunmurry House. We searched all these beds carefully for 

 fossils, but without success. In the Dublin Museum, however, are 

 specimens of Illcenus Bowmani, Salt., and Leptcena quinquecostata, 

 M"Coy, which obviously come from the red beds. 



The red shales become more sandy above, and are succeeded by 

 compact grey and greenish micaceous grits which form the main 

 mass of Dunmurry Hill. These beds all have a general S.E.-and- 

 N.W. strike, while that of all the beds east of the fault is N.E.-and- 

 S.W. They dip south-west at an angle of 25° to 35°. 



At the extreme northern foot of Dunmurry Hill, by the hedge, 

 there occurs at one point an exposure of Chair limestone, and east 

 of it a patch of greatly altered lava with porphyritic felspars. We 

 came to the conclusion that these were not in place. 



Grange Clare Hill is formed entirely of green and grey micaceous 

 grits with occasional shaly bands. These beds are thrown into a 

 series of folds, as shown by the dip-angles. 



V. Summary op Conclusions as regards the Sedimentary Rocks. 



We found no palseontological evidence to determine the age of the 

 beds forming Dunmurry and Grange Clare Hills, and the two fossils 

 in the Dublin Museum are insufficient for the purpose, as, although 

 they occur in the neighbouring Chair limestone, they also range up 

 into beds of Yalentian age. It seems to us improbable that beds 

 so absolutely different lithologieally should be deposited contempora- 

 neously in areas so near together as the Chair and Dunmurry Hills, 

 and we are therefore disposed to think that the Dunmurry beds are 

 of Silurian age. The grit of Dunmurry resembles the grit previously 

 mentioned as exposed in a small quarry ± mile east of the Chair 

 Farm, and it is possible that the red and black shales of Dunmurry, 

 as well as the Staurocephalus-Wmestoue, may be present in the drift- 

 covered tract of land between the Chair Farm and the grit quarry. 



We would, therefore, group the sedimentary rocks of the inlier as 

 follows : — 



