stumps, filled with sand and mud, are common in the Coal Measures,
and in them one sometimes finds leaves and stems, land shells, and
the bones of little reptiles of the time which made their home
there.

It is important to note that some of these gigantic lycopods,
which are classed with the CRYPTOGAMS, or flowerless plants, had
pith and medullary rays dividing their cylinders into woody
wedges. These characters connect them with the PHANEROGAMS, or
flowering plants. Like so many of the organisms of the remote
past, they were connecting types from which groups now widely
separated have diverged.

Gymnosperms, akin to the cycads, were also present in the
Carboniferous forests. Such were the different species of
CORDAITES, trees pyramidal in shape, with strap-shaped leaves and
nutlike fruit. Other gymnosperms were related to the yews, and it
was by these that many of the fossil nuts found in the Coal
Measures were borne. It is thought by some that the gymnosperms
had their station on the drier plains and higher lands.

The Carboniferous jungles extended over parts of Europe and of
Asia, as well as eastern North America, and reached from the
equator to within nine degrees of the north pole. Even in these
widely separated regions the genera and species of coal plants are
close akin and often identical.

INVERTEBRATES. Among the echinoderms, crinoids are now exceedingly
abundant, sea urchins are more plentiful, and sea cucumbers are
found now for the first time. Trilobites are rapidly declining,