46 THE ROMAN COMAGMATIC REGION. 
orthoclase, differ widely in texture and mode from the other rocks of the region to 
which the name tephrite is applied, and which contain abundant labradorite, prac- 
tically no orthoclase, few and small leucite phenocrysts, and with a dark-gray 
ground mass. For these reasons the name of leucite-trachyte is the more appropriate. 
PAGLIAL PROCENOSEPULAS-KOSE. I. 6-5. 2. 3. 
Megascopic characters. Light gray, compact, porphyritic. Leucite phenocrysts not very 
abundant, 5 to 20 mm. in diameter, fragmentary, and with crystal planes, not many inclusions. 
Feldspar phenocrysts, few, some 10 to 20 mm. long, stout prismatic, mostly small and inconspic- 
uous; augite phenocrysts, very few, very small, prismatic, black. Groundmass: medium gray, 
aphanitic. 
Microscopic characters. Holocrystalline, megaporphyritic, megaphyric and microphyric, 
dopatic. Megaphenocrysts: about 15 per cent, leucite, labradorite, orthoclase, augite. Micro- 
phenocrysts: about 6 per cent, leucite. Groundmass: about 80 per cent, trachytic fabric; 
orthoclase, labradorite, augite, nephelite, magnetite. 
Orthoclase, Or 5 Ab 3 . Phenocrysts: about i per cent, 10 to 20 mm., subhedral, stout pris- 
matic. Groundmass: about 50 per cent, 0.05 to 0.20 mm., anhedral, prismatic, arrangement 
subparallel. 
Labradorite, about AbiAn 2 . Phenocrysts: 3 per cent, glomerophyric, clusters of anhedral, 
stout prisms, clusters 0.5 to 2.0 mm. in diameter, commonly twinned. Groundmass: about 
15 per cent, 0.05 to 0.20 mm., anhedral, prismatic, arrangement subparallel. 
Leucite. Megaphenocrysts: 10 per cent, 5 to 20 mm., subhedral, mostly fragmentary, 
equant to irregular, few inclusions, of augite and labradorite. Microphenocrysts : about 6 
per cent, o.i to 0.2 mm., anhedral, equant, inclusions rare. 
Augite. Phenocrysts: about 2 per cent, 0.5 to i.omm., anhedral to subhedral, pris- 
matic, pale greenish-gray, inclusions few. Groundmass: about 4 per cent, 0.02 to 0.05 mm., 
anhedral, prismatic, colorless. 
Nephelite. Groundmass: about 6 per cent, anhedral, interstitial cement. 
Magnetite. Groundmass: about 2 per cent, o.oi to 0.02 mm., anhedral, equant. 
Analysis and norm as on p. 43. 
Type specimen from below castle, Proceno, northwest of Lake Bolsena, Vulsinian District. 
I. 6. 1. 3. Sabatinal Beemerose [Leucite-Phonolite, Sabatino Type]. 
Megascopic characters. Rocks of this type are very light gray and markedly 
porphyritic, showing rather numerous large phenocrysts of leucite, with many 
minute ones of augite. The leucite phenocrysts, which vary in diameter from 2 to 
10 mm., are usually anhedral and with irregular outlines, though they sometimes 
show crystal planes. In the type specimen they are slightly yellowish, but they may 
be normally considered as colorless. The small augites are stoutly prismatic, and 
very dark green or black. The ash-gray groundmass is quite aphanitic. 
Microscopic characters. In thin section the large leucite phenocrysts show the 
twinned structure very well. The augite phenocrysts are subhedral, in stout prisms, 
of a rather deep olive-green, and with the optical characters of aegirite-augite. 
The groundmass is holocrystalline and shows a confused fabric, due to the 
diverse arrangement of the short, stout prisms of alkali-feldspar of which it is very 
largely composed. These are either twinned according to the Carlsbad law, or more 
often simple crystals, and lime-soda feldspar seems to be entirely wanting. There 
are also many small, round anhedra of leucite, which are not infrequently changed to 
