With
them there is now a new experiment in the stalked Echinoderm, the
Blastoid, an armless type; but it seems to have been a failure.
Sea-urchins are now found in the deposits, and, although their
remains are not common, we may conclude that the star-fishes were
scattered over the floor of the sea.
For the rest we need only observe that progress and rich
diversity of forms characterise the other groups of animals. The
Corals now form great reefs, and the finer Corals are gaining
upon the coarser. The Foraminifers (the chalk-shelled, one-celled
animals) begin to form thick rocks with their dead skeletons; the
Radiolaria (the flinty-shelled microbes) are so abundant that
more than twenty genera of them have been distinguished in
Cornwall and Devonshire. The Brachiopods and Molluscs still
abound, but the Molluscs begin to outnumber the lower type of
shell-fish. In the Cephalopods we find an increasing complication
of the structure of the great spiral-shelled types.
Such is the life of the Carboniferous period. The world rejoices
in a tropical luxuriance. Semi-tropical vegetation is found in
Spitzbergen and the Antarctic, as well as in North Europe, Asia,
and America, and in Australasia; corals and sea-lilies flourish
at any part of the earth's surface.
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