PETROGRAPHY. 129 
is met with as a flow at the small hill of San Francesco, southeast of Ceccano, in the 
Hernican District. This, however, is lighter in color, though it presents much the 
same, but smaller, phenocrysts of olivine and augite. Its groundmass is much finer 
grained, with numerous small prismoids of augite, but little olivine, magnetite 
grains, and no biotite, embedded in a colorless base. This last is seen to be in part 
of plagioclase, in small, short laths, and in part isotropic, and possibly leucite. 
Unfortunately no analysis has, as yet, been made of this rock, the specimens of 
which are not very fresh, so that its assignment to this type is but provisional and 
somewhat doubtful. 
Name. The name of the subrang to which this type belongs, III. 7. 3. 2, is 
derived from Montefiascone, the chief town in the neighborhood, and the typal 
adjective is derived from the hamlet of Fiordine, near which the type specimen 
analyzed was found. 
The type from Fiordine has not yet been described, it would appear, but under 
the prevailing classifications there is no doubt that it would be called a leucite- 
basanite, though the amounts of leucite and feldspar are not very great. The type 
from San Francesco, near Ceccano, which is very doubtfully referred here, is called 
by Viola a feldspar-basalt, though he also mentions a leucite-basanite from San 
Francesco, apparently a distinct rock, of which I found no specimens. In the 
absence of an analysis, and in view of the difficulty as to deciding whether leucite 
is present or not in the fine-grained groundmass, the name feldspar-basalt would 
seem to be appropriate for this last occurrence, which, if found to be leucitic and by 
chemical analysis shown to belong to the subrang III. 7. 3. 2, could be called 
ceccanal fiasconose. 
FIORDINAL FIASCONOSE. III. 7. 3. 2. 
Megascopic characters. Dark gray, compact, highly porphyritic. Augite phenocrysts 
abundant, 2 to 10 mm., prismatic, equant and irregular, black or dark green. Olivine pheno- 
crysts common, 2 to 20 mm., equant, olive-green. Groundmass: dark gray, aphanitic. 
f -* Microscopic characters. Holocrystalline, magnophyric, dopatic. Phenocrysts: about 30 per 
cent, augite, olivine. Groundmass: about 71 per cent, xenomorphic granular, augite, leucite 
anorthite, olivine, biotite, magnetite, apatite. 
Anorthite. Groundmass: about 13 per cent, anhedral, poikilitic areas, twinned, inclosing 
leucite, augite, olivine, magnetite. 
Leucite. Groundmass: about 17 per cent, 0.02 to o. 10 anhedral, equant, round sections, 
clear, free from inclusions, inclosed poikilitically in the anorthite. 
Nephelite. Groundmass: about 3 per cent, anhedral, interstitial. 
Augite. Phenocrysts: about 25 per cent, 0.05 to 20.0 mm., euhedral to subhedral, pris- 
matic, equant, and irregular, often fragmentary, pale gray, few inclusions of magnetite. Ground- 
mass: about 25 per cent, 0.02 to 0.50 mm., anhedral, equant and prismatic, very pale gray. 
Olivine. Phenocrysts: about 10 per cent, 0.5 to 20 mm., subhedral to anhedral, equant 
and tabular, colorless, only slightly altered on edges, few inclusions of magnetite. Ground- 
mass: about 5 percent, 0.05 to 0.50 mm., euhedral to subhedral, equant, prismatic and tabular, 
colorless, very slightly altered. 
Biotite. Groundmass: about 2 per cent, o.i to 0.5 mm., anhedral, as irregular, inter- 
stitial patches, often inclosing augite, olivine, and magnetite poikilitically, brown. 
Magnetite. Groundmass: about 2 per cent, o.oi to 0.05 mm., anhedral, equant. 
