Vol. 58. ] THE FOSSILIFEROUS SILURIAN BEDS OF KERRY. 259 
rocks are of all lengths up to 5 inches, and generally stand out 
prominently from the weathered surface. They are sometimes solid, 
but occasionally contain irregular hollows, which are often lined 
with chalcedony or with small, though often well formed, quartz- 
crystals. We have no theories to offer in regard to the forma- 
tion of these nodules, but may remark that we have not detected 
spherulitic structure in connection with them. ‘The rock exposed 
at the point north of Mill Cove is pale purplish-white in a hand- 
specimen, with many small dark nodular lumps. When viewed in 
ordinary light under the microscope, patches. are observed which 
resemble xenoliths, but in polarized light these merge more or less 
completely into the surrounding matrix, and are seen to consist 
of quartz and felspar intergrown in a micropecilitic fashion. No 
phenocrysts were met with. 
A micropeecilitic character is also strongly marked in two other 
sections of rhyolite from the same locality: in one case micropceci- 
litic patches are thickly strewn throughout the section, in the other 
almost the whole of the groundmass is micropeecilitic. 
Some of the rhyolites from the Foilwee promontory also show 
numerous small micropecilitic patches in the groundmass. 
(2) Banded rhyolites.—These are the most plentiful and 
important of the lavas. The great mass of the Clogher-Head 
rhyolite is markedly banded in its eastern portion near the Min- 
naunmore Rock; while in the western exposures near the headland 
the banding is not, as arule, so well marked. Next tothe Clogher- 
Head mass the most important banded rhyolite is the upper part of 
the Foilwee or Poulnakeragh flow. In the banded variety of the 
Clogher-Head rhyolite, the bands are seen under the microscope to 
be identical in character with many of the small nodules, and to 
consist of quartz and felspar intergrown in a micropeccilitic fashion, 
while the rest of the section is cryptocrystalline. A considerable 
amount of epidote is developed in connection with these bands. 
Some sections of the Poulnakeragh rock show very numerous 
small spots in the groundmass, which are free from sericitic mica, 
and appear black in polarized light. Mr. Harker, to whom we 
submitted a section, says that these spots seem to be micropeecilitic 
areas, and drew our attention to the occurrence of similar spots in 
rhyolites described by him from Caernarvonshire* and from Dufton.” 
Among the various types of rhyolites exposed in the fine coast- 
section due west of Carhoo village, is a compact purple rhyolite 
which presents a banded appearance in a hand-specimen, owing 
to the occurrence of elongated lenticular patches marked out by 
the abundance of brown iron-oxide. In section, orthoclase-pheno- 
erysts are seen to be plentiful, and the groundmass shows excellent 
flow-structure round them. The rhyolite seen south of Carhoo is 
also occasionally banded. 
1 « Bala Volcanic Area of Caernarvonshire’ Sedgwick Prize Essay for 1888 
[1889] pp. 22-23. 
2 Quart. Journ. Geol. Soc. vol. xlvii (1891) p. 519. 
Q.5.G.8. No. 230. - 
