724 
Proceedings of the Royal Irish Academy. 
Summary. 
Creggaunbaun and the Killary or Slieve Partry Silurian Basins. 
The statements in reference to these rocks are : — 
1st. All the rocks between the Killary and Clew Bay, county . 
Mayo, belong to the Silurians. My TJmalians (Croagh Patrick and 
Boolough series) being sheared Silurians, and consequently that my 
boundaries are myths. 
2nd. The green slates in small exposures to the north of the Killary 
and in the Rossroe promontory are also Silurians. 
3rd. The fossil evidence proving that the Umalians are equivalent 
to the Ordovicians is valueless, as the fossils have been wrongly 
determined. 
4th. The gneiss and schist north of Kilbride Bay, Lough Mask, are 
only a sheared portion of the fossiliferous Silurians to the northward. 
My replies are : — 
1. The Creggaunbaun series can be distinctly seen lying uncon- 
f ormably across the upturned Umalians in different places ; while the 
Silurians between Lough Mask to the east and the Atlantic to the 
west, in various places in connexion with their northern boundary, 
strike more or less obliquely to the Umalians ; they all dipping south- 
ward at low angles, while the Umalians are from vertical to rolling at 
low angles ; also the basal conglomerates and pebbly grits contain 
more or less debris of the rocks in the country to the northward ; also 
the traps and faults so numerous in the Umalians, although they come 
up to the northern boundary of the Silurian basin, never enter it. 
2. The green slates in the small patches north of the Killary, stand 
at high angles, while the overlying Silurian dip north at low angles. 
The green slates in the Rossroe promontory are evidently brought into 
their present position by a down-throw, to the northward, fault, as 
can easily be proved if this fault is traced eastward into Slieve 
Partry. 
3. The age of the Umalian fossils was determined by such authori- 
ties as Harkness, W. King, and W. H. Baily, after years of study of 
the Ordovician types, of not only Ireland, but of the world. 
4. The gneiss and schist north of Kilbride Bay is brought into its 
present position by a fault, probably an upthrust. The fossiliferous 
rocks to the northward are largely made up of their debris ; also this 
