294 STRUCTURE OF ARVONIAN ROCKS FROM PEMBROKESHIRE. 
9. Near Bryn, S.E. of Treglemais(p.290).—A ppears macroscopically 
to be a quartz-felsite of a greenish-grey colour; it is much fissured. 
Exhibits in thin section numerous fragments of preexisting rocks 
which have been caught up in a quartz-felsite, the confused fluxion 
structure of which characterizes a .certain type of these rocks. 
Among the fragments thus enclosed are those of a rock like No. 8, 
of some hilleflintas like Nos. 1 & 3, with numerous crystals and 
fragments of orthoclase and plagioclase, also angular quartz and 
erains of magnetite. Crystalline quartz occupies numerous fissures 
and nests in the mass. 
(For Discussion on this paper, see p. 325.) 
