PETROGRAPHY. 
account of the comparative rarity of multiple twinning in the plagiodase. The 
subhedral leucite phenocrysts carry few inclusions and call for no comment, except 
that they are not very abundant. The greater part of this mineral is in the ground- 
mass, in very small, spheroidal anhedra, these and the phenocrysts both showing 
twinning lamellae with the selenite plate. The augite phenocrysts and the ground- 
mass prismoids are of the usual variety, subhedral and very pale gray in color, with 
few or no inclusions. Biotite exists only as small tabular phenocrysts, of a pale- 
brown color, pleochroic, and for the most part deeply altered. The amount of 
magnetite is small, and the greater part is found as small anhedral grains scattered 
through the groundmass, though there are a few small phenocrysts. A little apatite 
is present in small prisms. Olivine is wanting, and neither nephelite nor glass could 
be detected. 
Chemical Composition. A specimen of this type from below Orchi was chosen 
for analysis, as it seemed to be fresher than those from near Teano. The analysis 
has not hitherto been published. 
Chemical Composition of Teanal Ciminose-auruncose [Leucite-trachyte]. 
I. 
I. 
SiOa 
co. 86 
0.848 
CO 2 
none 
Al a O 3 
18.48 
.181 
TiO 2 
Fe 2 O, . 
4.O2 
.025 
ZrOj 
o 02 
FeO 
2 .4.C 
.048 
P,Oc.. 
o 46 
MgO. . 
2 . CS 
.064 
SO, .. 
CaO 
7. 77 
. 1 20 
MnO. 
nd 
Na 2 O 
2. 2? 
.031; 
BaO 
0. 17 
K 2 O 
7TC 
H 2 O+ 
I . ^1 
99.84 
H a O- 
o. 16 
Teanal auruncose [leucite-trachyte]. Below Orchi, Auruncan District. Washington, analyst. 
Norm. 
Ratios. 
Or 
42.81 ) 
Ab 
6.8 r [-68.80) 
An 
..19.18) 'r 
Ne 
6.25 6.25 ) 
Di 
..13.22? - 
01 
. Jolt 14 ' 26 
Mt 
C . 80 ) o 
11 . 
. I 08$ 7^8 
Ap.. 
I . O2 I . O2 
Rest 
98.11 
X . 86 
Class. 
75-05 
23.06 
Order . 
Sal 
'Fern 
F 
'L 
Rang. . . 
Subrang 
' + Na 2 O' 
CaO' 
3.26 
1.62 
K 2 O' 
'Na 2 O' 
99-97 
The general similarity of this analysis to that of the orvietal type next to be 
described is quite close. The analysis of 'the teanal auruncose shows that this 
type is well within the borders of class, order, and subrang, but so close to 
