THE VOLCANOES AND ROCKS OF PANTELLERIA 689 
phosphoric oxides, and partly because of certain features which 
will be discussed later. They indicate, however, that the silica 
is probably lower in some of these trachytes than in my analyzed 
specimens. 
The norms of A, B and C are given below: 
A B G 
Oe. 24.0 ORS Rae aioe ee 3.90 5-58 yf 1) 
OLE tre sei oo euersttes oes 25.58 20nr3 25.02 
NDEI ea I cea hGie mare outs Bs 56.59 53-97 44.01 
BAIN ee eee ee ee 1.67 3.06 0.83 
ID 5.15 Cate Ceres Olona ae eee 4.83 2.48 1.94 
EI ARNT ie teks Sos sie wie wie Be 1.59 1.96 0.50 
JWI 5, oad Oe lgtece eee NOE eee ere 3.02 Bott say 
Jatin. 5 Se Bee eee ee ee Ren luge 0.604 
ar tete ahah theists. s 2.28 hs OF pate 
IN Dora) o of caG.ccon ES eae 0.34 0.67 0.34 
99.80 98.83 98.08 
[ROR vo oO GEO OCHO oe ee 0.64 0.93 DyaN2 
100.44 99.76 100.20 
The magmatic symbol of A is I(II).5.1.4, that of B is 
II) .”’5.1’’.’"4, and that of C is I(II).4.1.(3)4, using the nota- 
tion recently proposed* to indicate the exact position of a rock 
magma in each division of the Quantitative System. The first 
two are in nordmarkose, in the persalane class but transitional 
toward dosalane, and hence are strictly to be called umptekose- 
nordmarkose, B not being as centrally placed in the other divisions 
as A. The excess of silica is so small as to be negligible. The 
Zichidi rock also falls in the same place as regards the class, but 
is in order 4, and its dosodic subrang is transitional toward the 
sodipotassic one, so that it is a liparose-kallerudose. Here the 
amount of normative quartz is notable, indicating its tendency 
toward the pantelleritic trachytes. It is to be noted that these 
trachytes (and the basalts) are the only Pantelleria rocks which 
show normative anorthite, so that, in spite of the presence of 
aegirite-augite, no acmite appears in the norm. 
™ Cross, Iddings, Pirsson, and Washington, Jour. Geol., XX (1912), 554. I use 
the sign’’ to indicate that the position is intermediate but not transitional; that is, 
between the central portion and the transitional border. 
