PETROLOGY. 165 
phlegrose (I. 5. 1.3), of both the ischial and cumal types [trachyte], and vulsinose 
(I. 5. 2. 2), of the bolsenal type [vulsinite]. Apparently the majority of the rocks 
belong to the dosalane class. Of this the subrang ciminose (II. 5. 2. 2) is rare, 
while auruncose (II. 5. 3. 2) is abundant, two types [leucite-tephrite] being repre- 
sented, both of which are leucitic and one carrying considerable biotite. The 
subrang shoshonose (II. 5. 3. 3), while not abundant, is important, as the monfinal 
type of this magma [biotite- vulsinite] forms the central mass of Monte Santa Croce. 
Viterbal vicose (II. 6. 2. 2) [leucite-tephrite], with abundant large leucite pheno- 
crysts, is common, probably as much so here as at the Ciminian District. While 
no rocks falling in braccianose, vesuvose, or in the salfemane class were collected 
by myself, it would seem from some of the published descriptions that such do 
occur, and probably rather abundantly, in the western part of the district. These 
are leucitic and presumably of types found elsewhere [leucite-tephrite and leucitite]. 
In addition some non-leucitic types [basalts] are described, but in such vague terms 
that nothing definite can be established as to their magmatic character, except 
that they are almost certainly in dosalane, and probably in the perfelic order 
germanare. 
From these meager data it is at least clear that the rocks of the Auruncan 
District are very diverse in character, the magmatic range being almost as great 
as at the Vulsinian District, and both leucitic and non-leucitic types being abundant. 
But it is evident that much more study is needed before this volcano can be satis- 
factorily characterized. 
CAMPANIAN DISTRICT. 
This district embraces three quite distinct centers of volcanic activity; the 
Vesbian Volcano, including the older Somma and the later Vesuvius, the volcanic 
complex of the Phlegrean Fields, and the island of Ischia, which is essentially the 
Epomeo Volcano, with its parasitic cones. The rocks of Vesuvius and Somma 
are remarkably uniform, most of them falling in braccianose (II. 7. 2. 2), with 
fewer in jugose (III. 7. 2. 2) and vesuvose (III. 8. 2. 2), several different types 
[leucite-tephrite] being represented. The Phlegrean Fields and Ischia are simi- 
larly uniform, though here the character of the magmas is quite different. In these 
two subdistricts the rocks are practically all in persalane, and by far the most 
predominant subrang is phlegrose (I. 5. i. 3), which is represented by several 
texturally different types [trachyte]. Bolsenal vulsinose (I. 5. 2. 2), pulaskose 
(I. 5. 2. 3), and monzonose (II. 5. 2. 3) [vulsinite] are found, but in small amounts 
comparatively, and some leucitic types of unknown subrangs occur, but always as 
blocks and in negligible quantity. 
The Campanian District, then, is composed dominantly of but two subrangs, 
phlegrose and braccianose, the points of eruption of these being distinctly 
separated, though these very diverse magmas have been erupted simultaneously 
at times. 
