36 LTT JOLIN ALTE OLN GEOL OGNVA 
Megascopically they are compact, fine-grained rocks of a 
rather dark, slightly bluish gray color, the groundmass showing 
to the naked eye comparatively few small phenocrysts of dull 
white plagioclase with, at Chelona, a few hornblende needles, 
and at Oros and Mt. Kouragio a very few rounded colorless 
quartz grains. They present, on the whole, a decidedly phono- 
lite-like appearance, the resemblance being heightened by the 
lamellar structure seen on the top of Mt. Oros and at Agio 
Somatos, and by the sound which many of them give on being 
struck with a hammer, notably the rock from the south end of 
Mt. Kouragio. The augite-andesite: of Agio Somatos differs 
sightly from the others in being rather granular in structure, 
and containing more slender hornbiende needles. These rocks 
do not decompose readily and are quite fresh, except in the case 
of two specimens from Mt. Oros, which are reddish brown in 
color. 
Under the microscope these rocks show an abundant, often 
hyalopilitic groundmass, with flow structure well marked; the 
glass base, which is clear and colorless, except in the Mt. Kou- 
ragio rocks where it is light brown, being in relatively small 
quantity. This glass base seems to be more abundant in the 
hypersthene-andesites than in the augite-hypersthene-andesites, 
in one or two of the latter from Mt. Oros the groundmass being 
almost holocrystalline, with only traces of glass, and in those 
from Mt. Kouragio the groundmass being rather basaltic with 
many lathes of plagioclase and hypersthene, and very little 
interstitial glass base. 
The microlites and small crystals of the groundmass are 
mainly hypersthene, with fewer of plagioclase, many magnetite 
grains, and in the augite-hypersthene-andesites very many small, 
approximately equidimensional crystals of nearly colorless augite. 
The small hypersthene needles vary in length from 0.02 to 
0.1 mm., their diameter being as a rule about one-fifth of the 
length. They all have parallel extinction, show low domal or 
pyramidal terminations, and are generally cracked transversely. 
They are clear and almost colorless, of a very faint greenish 
