SKETCH OF AVAGINA AND METHANA. 41 
The large plagioclase phenocrysts are quite fresh and clear 
and many show a “‘network”’ core of glass. Twinning lamella are 
not very common, and, as the angles observed were small, the 
phenocrysts are referable to labradorite, though in some cases 
they seem much more basic. 
The few quartz sections are rounded and irregular, perfectly 
clear but much cracked and with few inclusions of glass. One 
small perfectly hexagonal section was seen. A few small color- 
less prismatic augite phenocrysts were noted as well as some 
dark green biotite tables, one of which contains a colorless 
zircon. 
Hlornblende-Hypersthene-Dacite.—\t would be more in accord- 
ance with Zirkel’s definitions to call these rocks quartz-pyroxene- 
andesites since he reserves the name dacite for the more acid or 
quartz-bearing hornblende or biotite-andestites.*. On the other 
hand Rosenbusch? does not put these limits on the dacites, but 
includes among them very acid or quartz-bearing pyroxene- 
andesites. I am inclined to favor his view since the presence or 
absence of quartz or superabundant silica seems to me a consid- 
eration of much more weight than the nature of the ferro-mag- 
nesian silicate, and this, together with the presence of green 
hornblende in the most typical specimens, has decided me in 
giving them the name they here bear; they being called as they 
are owing to the greater abundance and importance of the hyper- 
sthene over the hornblende, none of the latter appearing as a 
groundmass constituent. 
These rocks are the most abundant of any species on Meth- 
ana, most of the mountain masses around Mt. Chelona being 
formed of them. Specimens were collected and examined from 
near Vromo, from the ridge south of Mt. Chelona, Mt. Chorsa 
to the northwest of Chelona near Panagia on the northwest 
coast, and from the neighborhood of Kosona, both near the town 
and between it and Mt. Chelona; and, further, my notes show 
that the rock along the coast between Kosona and Vromo 
*ZIRKEL. Op. cit. II., p. 560. 
2 ROSENBUSCH, Mikr. Phys. II., 1887, p. 634. 
