y passed beneath the waters, instead of a
re-elevation of the land, however, we may suppose that the shallow water
was gradually filled with silt and debris from the land, and a fresh
forest grew over it.

* The civic authorities of Glasgow have wisely exposed and
protected this instructive piece of Coal-forest in one of
their parks. I noticed, however that in the admirable
printed information they supply to the public, they describe
the trees as "at least several hundred thousand years old."
There is no authority in the world who would grant less than
ten million years since the Coal-forest period.

These changes are reflected in the progress of marine life, though their
influence is probably less than that of the great carnivorous monsters
which now fill the waters. The heavy Arthrodirans languish and
disappear. The "pavement-toothed" sharks, which at first represent
three-fourths of the Elasmobranchs, dwindle in turn, and in the
formidable spines which develop on them we may see evidence of the great
struggle with the sharp-toothed sharks which are displacing them. The
Ostracoderms die out in the presence of these competitors. The smaller
fishes (generally Crossopterygii) seem to live mainly in the inland and
shore waters, and advance steadily toward the modern types, but none of
our modern bony fishes have yet appeared.

More evident still is the effect of the new conditions upon the
Crustacea. The Trilobite, once the master of the seas, slowly yields
to the stronger competitors, and the latter part of the Carboniferous
period sees the last genus of Trilobites finally extinguished. The
Eurypterids (large scorpion-like Crustacea, several feet long) suffer
equally, and are represented by a few lingering species. The stress
favours the development of new and more highly organised Crustacea. One
is the Limulus or "king-crab," which seems to be a descendant, or near
relative, of the Trilobite, and has survived until modern times. Others
announce the coming of the long-tailed Crustacea, of the lobster and
shrimp type. They had primitive representatives in the earlier periods,
but seem to have been overshadowed by the Trilobites and Eurypterids. As
these in turn are crushed, the more highly organised Malacostraca take
the lead, and primitive specimens of the shrimp and lobster make their
appearance.

The Echinoderms are still mainly represented by the sea-lilies. The
rocks which ar