144 Scientific Proceedings, Royal Dublin Society. 
E.N.E. and W.S.W. synclinal and anticlinal curves as indicated in 
the accompanying section which is only intended to represent 
their general position and relations. 
In south-east Wexford lying unconformably on the Cambrian, 
are rocks of the Dark Shale series, and over the latter are rocks of 
the Ballymoney series. But to the N.W. in the Shevenaman 
district, county Tipperary, and further westward in the Galtees, 
county Limerick, there is also an Upper series. This is the case 
also in Slieve Phelim, northward of the last and in Slieve Arra ; 
as also in the east portion of Slieve Bernagh, and in the Cratloe 
Hills on the other side of the Shannon, in the last of which at 
Ballycar there is a colony of Silurian (Upper Llandovery) fossils 
—north of the last in the west portion of Slieve Bernagh the 
Dark Shales and Ballymoney series are represented, while still 
farther north in Slieve Aughta, there seems to be in addition a 
slight thickness of rocks belonging to the Upper series. 
To the N.W. of Slieve Aughta in west Galway, and8.W. Mayo, 
the representatives of the Dark Shale series (Doolough beds) and 
Ballymoney series (Croagh Patrick beds) lie, as it would appear 
conformably, on an anticlinal of the Cambrian rocks. The age 
of the latter can scarcely be disputed; they constitute a series of 
strata at least 8,000 feet in thickness, which underlie the Doolough 
beds. The Doolough beds both lithologically and in their fossils 
represent the Dark Shale series, which, elsewhere in Ireland, occurs 
at the base of the Cambro-Silurians; they seem to be equivalents of 
the Llandeilos of England which are taken by Dr. Ramsay to be 
the base of the English Cambro-Silurians.* Farther N.W. in 
Erris or N.W. Mayo, similar rocks lie as it would seem uncon- 
formably on Cambrians. Between the Cambrian exposures of 
Erris and of West Galway, the district of Cambro-Silurians dis- 
plays a great thickness of those rocks, and it is quite possible that 
the Upper series is there partly represented; butas all the Cam- 
brian and Cambro-Silurian, and indeed a considerable area of 
Silurian, are more or less metamorphosed, it is difficult to separate 
the rocks into the different groups. If the suggestions in refer- 
ence to Erris are correct, it is probable that in N.W. Donegal, 
Cambrians crop out somewhere from under the Cambro-Silurians, 
It will be seen then from the above, that rocks of the Upper 
* Sir Charles Lyell would make the base lower down. 
