Vol. 58. ] THE FOSSILIFEROUS SILURIAN BEDS OF KERRY. 263 
The phenocrysts are of plagioclase, sometimes fairly fresh, and 
giving (in the case of the Clogher-Head rock) a maximum extinction- 
angle of 24° (labradorite), but generally much altered. In the 
Foilwee rock no phenocrysts occur. There is very little trace of 
any ferromagnesian constituent, but the Redcliff-Cove rock contains 
a few small patches of serpentine, which may represent altered 
rhombic pyroxene. Needles of apatite are seen in the Mill-Cove 
rock. Vesicles sometimes occur : in the Clogher-Head rock they are 
mainly filled with chlorite, but have brilliant epidote round the 
margin. The Coosaneal rock contains a great number of small 
irregular cavities, occupied by chlorite and chalcedony. 
(2) The labradorite-porphyrite.—This rock is seen only 
in the inlet of Foilnamahagh, where it is bounded by a fault on either 
side. It is very similar in appearance to the porphyrites of Eastern 
Jreland seen at Kildare, Lambay, and Portraine. There is little to 
show whether it is contemporaneous or intrusive; the fact that its 
upper surface is amygdaloidal might be regarded as a small piece 
of evidence in favour of its contemporaneity, while its difference in 
character from all other rocks of the district to some extent lends 
colour to the view that it is an intrusive. 
The groundmass shows numerous felspar-laths giving a maxi- 
mum extinction-angle of under 10°, and probably to be referred to 
oligoclase. The spaces between them are filled up with a fine- 
grained, much iron-stained material. The phenocrysts consist of 
large plate-like crystals of labradorite, which are fairly fresh and 
reach a length of three-quarters of an inch or more. Large patches 
of magnetite occur, which appear to have been developed in relation 
to destroyed augite-crystals. 
(3) The quartz-porphyry.—tThis rock forms a small dyke in 
the inlet of Coosgorrib, on the west side of Smerwick Harbour. 
The groundmass shows quartz-grains and numerous flakes of 
muscovite, which are arranged with their long axes parallel one to 
the other. Numerous phenocrysts of quartz occur, commonly crushed 
and cracked. Some are just cracked, others have the cracked 
fragments displaced and the groundmass appearing between. them. 
A few of the grains also show marked corrosion by the groundmass. 
Phenocrysts of orthoclase also occur. 
VI. Generat Summary anp ConcLusIONs. 
(1) The Smerwick Beds, though yielding no fossil evidence by 
which their age can be determined, are undoubtedly the oldest rocks 
in this area. It is probable that they are of Llandovery age, as they 
are conformably overlain by fossiliferous Wenlock-Llandovery beds. 
(2) All the fossiliferous rocks of the Clogher-Head inlier are of 
Silurian age. The majority of those exposed on the coast are 
of Wenlock or Wenlock-Llandovery age; the majority of those 
exposed inland are of Ludlow age. The Wenlock and Wenlock- 
