1238 
were also met with here. No olivine was found in the samples of 
the mediumgrained xenoliths examined. 
The xenoliths mentioned sub 4, found only in some specimens, 
are free from amphibole, just as those mentioned sub 3. They are 
characterized by a remarkable structure, large plagioclase-phenocry sts 
lying in a groundmass, consisting of smaller crystals of plagioclase, 
few ore-crystals and very few of augite and hypersthene. The 
latter in their turn are surrounded by a fine-crystalline mixture 
of the same minerals, whose constituents — with the exception of 
the small plagioclases — occur in a large number as inclusions 
in the plagioclases of the first and te second generation (PI. fig. 4). 
Zonary structure does not occur with these plagioclases or 
only in a small measure and without the alternation of basic 
and more acid zones, which distinguish them from those 
of the enclosing lava. The fine-crystalline groundmass is almost 
entirely absent in a narrow marginal zone of the xenolith where 
this is contiguous to the enclosing lava. Here we see a mixture of 
plagioclase, like those occurring everywhere in the xenolith as small- 
sized phenocrysts, together with the angite-, hypersthene-, and ore- 
crystals, which are seen only in small number in the central parts 
of the xenoliths as small phenocrysts. It appears then that pyroxene 
and ore are accumulated in the marginal zone. The structures 
described heretofore point to the fact that the crystallization of the 
xenoliths was still to take place for the most part, when they had 
already been taken up in the enclosing lava. In an early stage the 
plagioelases, the pyroxenes, and the ore-crystals of the second gene- 
ration have crystallized. The latter two have accumulated in the 
marginal zone of the xenolith. That the crystallization of the plagio- 
clases was the first to be finished here, is proved by the idiomorph- 
ous shape of the crystals relative to the pyroxenes in the marginal 
zone and the enclosure of plagioclase by pyroxenes, which occurs 
frequently here. In the central parts we see that the crystallization 
of the ore and of the pyroxene of the fine-crystalline groundmass 
had already begun during the crystallization of the plagioclases, 
some of which have grown into larger phenocrysts. Then followed 
the ultimate crystallization of the fine-crystalline groundmass, in 
which oceurs the plagioclase in rounded shapes, which points to a 
crystallization about simultaneous with that of the pyroxene. The 
plagioclases of the marginal zones are poor in or destitute of in- 
clusions and seem, therefore, to have erystallized before those of 
the central part of the xenolith, or the crystallization of the fine- 
crystalline groundmass has taken place in the marginal zone later 
