42 THE JOURNAL OF GEOLOGY. 
Limni are the same as at the former place; so that it is seen 
that the whole southern part of the peninsula (with the excep- 
tion of the district around Methone and Megalo Chorio), with 
much of the northwest, north and east are of these rocks. 
These do not show as much quartz as the other dacites, that 
from near Panagia especially being quite free from it, though its 
high silica content (64.83 per cent.) shows that it belongs here. 
Megascopically they much resemble the dacite of Anzeiou, being 
not very compact, light-gray rocks with very numerous pheno- 
crysts of plagioclase and hornblende, and fewer colorless or 
pinkish quartz grains. The Panagia specimen is much more 
compact and finer grained than the others, and phenocrysts are © 
smaller and less abundant. Endogenous enclosures are not 
rare, especially in the rock about Kosona. 
Under the microscope there are seen to be three distinct types. 
The Koséna specimens resemble much the hornblende-dacite 
of Anzeiou, the groundmass being typically hyalopilitic with 
colorless glass base. The hornblende is bright olive-green and 
perfectly fresh. Hypersthene, besides composing the great 
majority of the groundmass microlites, occurs in good-sized prisms 
as phenocrysts, which show all the optical characters already 
mentioned. Magnetite also occurs in large and small grains, but 
is rare as a true groundmass constituent. Some small colorless 
augite crystals are also seen. The plagioclase, which occurs 
chiefly in large poorly shaped phenocrysts, many with glassy 
‘‘net’’ cores, shows many twinning lamella; and the extinction 
angles of 25° and even less show that it is a bytownite rich in 
soda. They contain very many apatite needles. Biotite is 
very rarely seen in the slides, one large, clear, greenish gray prism 
being much corroded, and altered at the edges toa very coarse 
granular mixture of augite, plagioclase and magnetite. This 
alteration had chiefly taken place in the zone of the prisms and 
pinacoids, the basal plane being sharp and quite fresh. 
The second type is that presented by the specimens from the 
southern and western parts of Methana (with the exception of 
the Panagia specimen). These are characterized by a very dusty 
