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thin, slaty shales, cleaving in fissile plates parallel to the bedding.
They occur in bands up to several feet thick, and at times may
be readily mistaken for some of the more indurated bands in the
Haida shales. The rocks are characterized by the great number
of fossils they contain, the fossils consisting of flattened impres-
sions of the shells of ammonites and often crowding the laminz
in great profusion.

Limestones. The limestones of the southeast end of South
island are provisionally classified with the Maude argillites.
They consist of massive beds of light grey, partly crystalline
limestone, cut by irregular veinlets of recrystallized calcite,
from paper-thin sheets to 2 inches or more in thickness. They
are strongly bituminous, and give a markedly foetid odour when
struck.

Under the microscope the rock is seen to be made up of
rounded and sub-rounded granules of calcite, averaging 0-02 mm.,
without any appreciable matrix. Occasional grains of detrital
plagioclase are to be seen. Between the grains and in little
veinlets is black bituminous matter, and this also occurs along
suture-like cracks. Bitumen is almost wholly lacking in the
recrystallized veins.

On the south shore of Maude island, near the top of the
formation, bands of buff and grey, partly crystalline limestones
occur in beds up to 8 inches thick, containing, scattered through
them, groups of striated cubes of pyrite.

YAKOUN FORMATION.

Basalts.

These basalts are typically dark, purplish, or greenish, fine-
grained rocks, frequently porphyritic and sometimes amyg-
daloidal. Their altered nature is evident, even in hand
specimens, from the abundance of chlorite and other secondary
minerals developed.

Some of them have been recognized as flows or sills, but many
of the specimens examined were from fragments in agglomerates.

In thin sections the primary minerals seen are labradorite,

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