J^iLnoE—Siliiriau and Metaniorphic Rocks. 131 



name of this series from Llandovery, as on the published map, to 

 Wenlock. This series duly passes by uninterrupted sequence upward 

 into the Ludlow beds south and south-west of Leenane. 



8. The zone, which is of paramount worth in the interpretation 

 of the region, became recognizable in three bands in consequence of 

 anticlinal and synclinal plications and other dislocations {a) at Croagh 

 Patrick, {I) at Knockfadda and Cregganbaun, and {c) near 

 Toormakeady, Maam, and Kylemore. 



9. The recognition of the Wenlock rocks of Croagh Patrick in 

 Clare Island between two faults, hrought up thus amongst beds 

 similar to the red " Salrock Slate" of Ludlow Age, south-west of 

 Leenane, seems by inference to show that beds of this age exist 

 in Clare Island and along the coast west of Louisburgh, where 

 corresponding red slate and fine grits appear. I failed to find 

 fossils of any kind in this series. 



10. The series of coarse grits and conglomerates immediately 

 south-west of Leenane Hotel, represented as Wenlock strata on 

 the published map, contains black and dark grey slate, and chert 

 bands, which yielded Graptolites of Arenig or Lower Llandeilo Age. 

 This discovery obviously necessitated a radical change in the 

 representation. 



11. A series of highly cleaved lavas near Glenawough Lough — an 

 extension of the volcanic zone already known near the western 

 shores of Lough Mask — may also be mentioned as an interesting 

 element of the geology of the region not previously recorded. The 

 rocks are highly cleaved, and, equally with much of the sedimentary 

 group, were shown as ordinary metamorphic strata. 



By means of the foregoing fresh points of evidence the geology of 

 the region is reducible to a form more in accord with the natural 

 strati graphical arrangements and sequences recognizable elsewhere, 

 and even with most of the originally observed facts. The chief results 

 of the work have been mentioned in the Summaries of Progress of the 

 Survey's operations for the years 1893 and 1894. Hitherto the other 

 claims made on the time of the Survey have not permitted such 

 detailed examination of the Mayo area as would justify the issue 

 of maps containing considerable revisions. The Drift Map accompany- 

 ing the Department of Agriculture's book^ on the Soil Geology of 

 Ireland represents a revised view of the geology of the region ; and a 

 map is liere shown giving this in somewhat greater detail. Before 



By the present Author. 



P2 



