816 The American Naturulist. [October, 
that the greater portion of them are leucite-basanites. They all con- 
tain phenocrysts of augite, labradorite, olivine and magnetite in a 
groundmass which is sometimes a holocrystalline aggregate of oligo- 
clase, orthoclase, leucite and magnetite, and at other times of numerous 
leucites, small augites and iron oxides in a glassy matrix. The rocks 
are regarded as effusive types of lamprophyres (minettes or kersantites) 
a supposition which is the more probable from the fact that the effu- 
sives in the Lipari province are mainly feldspathic basalts, andesites, 
liparites and trachytes. Biotite and leucite are thought to be comple- 
mentary minerals—the former separating from a siliceous magma under 
considerable pressure, and the latter from a magma of the same com- 
position under surface pressure, under conditions favorable to the escape 
of the mineralizers fluorine and water. Leucite is not confined to 
rocks rich in potash, nor is it necessarily characteristic of these. Its 
place may often be taken by biotite. 
A Squeezed Quartz-Porphyry.—A squeezed quartz-porphyry 
- is described by Sederholm‘ as occurring at two places in the Parish of 
Karvia in Province Abo, Finland. In both it appears as dykes cut- 
ting granite. The rock consists mainly of microcline phenocrysts to 
which are often added growths of new microcline in optical continuity 
with the original crystals, phenocrysts of an acid plagioclase surrounded 
in many cases by microcline substance and quartz phenocrysts in a 
groundmass of orthoclase and quartz. The twinning of the microcline 
is more largely developed around quartz enclosures in the phenocrysts 
and near quartz veins than elsewhere in the crystals. The porphyritic 
quartzes occasionally retain their dehenhedral contours, but usually 
they are much deformed in outline and in their optical characteristics. 
Often the quartzes are so shattered that they now constitute lenticular 
areas of a quartz mosaic. The structure of the groundmass is in sev- 
eral types. In the most important one it consists of a micropegmatite 
of orthoclase and quartz containing shreds of chlorite, which in some 
cases are distributed so as to exhibit a fluidal arrangement. The gran- 
ite through which the porphyry cuts is a coarse grained porphyritic 
variety composed of oligoclase, biotite and hornblende. On the con- 
tact with the dyke rocks it is crushed and much epidote is developed 
in it. Under the microscope it presents the usual aspects of a dynam- 
ically metamorphosed rock. In his discussion concerning the name to 
be applied to the porphyry, the author quotes from a letter by Dr, Wil- 
liams in which the prefix ‘apo’ is defined as signifying that the rock 
+ Bull. Com. Geol. d’Finlande, No. 2, 1895. 
