116 OKDOVICIAN AND SILL T EIAN OF LOUGH NAFOOEY. [June 1914. 



(e) The Spilites (Pillow-Lavas). 



At certain localities, particularly in the neighbourhood of Cur- 

 raghrevagh hamlet, the spilite becomes coarsely porphyritic with 

 abundant large albites. Dr. Flett, to whom we showed these rocks, 

 compared them with those from the Plymouth and Newton Abbot 

 neighbourhood. 1 The only other point to add to the description 

 of these rocks given in the Kilbride paper, is the prevalence, 

 especially near the top of Bencorragh, of vesicles filled with epidote 

 or partly with epidote and partly with quartz. The average specific 

 gravity of eight examples of spilite was 2*74. 



VII. Comparison of the Bocks of the Kilbride, Loiioh- 

 Nafooev, and Killary Areas ; and Conclusions. 



Although no fossils except radiolaria were found associated with 

 the spilites and cherts of the Lough Nafooey area, there can be no 

 doubt that these rocks are the same series as those of the Kilbride 

 area, which are associated with black cherts and slates containing 

 Dixit/ mograptus extensus, and are therefore of Middle Arenig age. 

 No igneous rocks of Middle Arenig age were described by Mr. Maufe 

 and Mr. Carruthers from the Killary area, but they obtained an 

 abundant series of Middle Arenig graptolites in a bed of black 

 shale and chert at Bencraff, 6 miles west of Lough Nafooey. 



Limestone-breccias so characteristic of the Tourmakeady and 

 Glensaul areas, but completely absent at Kilbride, are met with 

 again at Lough Nafooey and in the Killary district. At Glensaul 

 they are associated with grits and other deposits containing" 

 Upper Arenig fossils (D.-Mrundo Zone). At Killaiy, too, they are 

 associated with strata considered to be of Upper Arenig age — 

 the Leenane and Rossroe Grits. 



The Silurian rocks of the Kilbride area all extend across into the 

 Lough Nafooey area ; and though, as their outcrop is followed, 

 certain differences in thickness and lithology are noticeable, the 

 general resemblance of the successive beds throughout the whole 

 extent of the outcrop is so great as to amount to identity. 



The Killary and Lough Nafooey rocks, on the other hand, contrast 

 somewhat strongly. The thick Red Sandstones and overlying 

 Annelid Grits of the Lough Nafooey area are unrepresented in the 

 Killary area. The next succeeding beds in both areas are similar, 

 consisting principally of calcareous strata with abundant Llandovery 

 fossils. In both areas these calcareous strata are followed by thick 

 arenaceous beds ; in the Lough Nafooey area there are grits overlying 

 flaggy beds containing Tarannon fossils, while in the Killary area 

 grits with Wenlock fossils overlie a coarse conglomerate, 



The highest beds in the Killary area, the Salrock Beds of Ludlow 

 age, are unrepresented in the Lough Nafooey area. 



The Kilbride and Lough Nafooey areas agree very closely in 

 regard to the intrusive rocks — felsites, lime-bostonites, coarse por- 

 phyrites, and dolerites. The felsites do not, however, occur in such 



1 See ' Geology of the Country around Plymouth & Liskeard ' Mem. Geol. 

 S.irv. Expl. Sheet 348 (1907) pp. 95-97 & pi. iv, fig. 1. 



