In the
first marine sediments of a calcareous nature which succeeded to
the Coal-measures (the magnesian limestones of the Permian), the
great group of the _Rugose corals_, which flourished so largely
throughout the Silurian, Devonian, and Carboniferous periods,
is found to have all but disappeared, and it is never again
represented save sporadically and by isolated forms.
[Footnote 19: A singular fossil has been described by Professor
Martin Duncan and Mr Jenkins from the Carboniferous rocks under
the name of _Paloeocoryne_, and has been referred to the Hydroid
Zoophytes (_Corynida_). Doubt, however, has been thrown by other
observers on the correctness of this reference.]
[Illustration: Fig. 117.--_Platycrinus tricontadactylus_, Lower
Carboniferous. The left-hand figure shows the calyx, arms, and
upper part of the stem; and the figure next this shows the surface
of one of the joints of the column. The right-hand figure shows
the proboscis. (After M'Coy.)]
[Illustration: Fig. 118.--A, _Pentremites pyriformis_, side-view
of the body ("calyx"); B, The same viewed from below, showing the
arrangement of the plates; C, Body of _Pentremites conoideus_,
viewed from above. Carboniferous.]
Amongst the _Echinoderms_, by far the most important forms are
the Sea-lilies and the Sea-urchins--the former from their great
abundance, and the latter from their singular structure; but the
little group of the "Pentremites" also requires to be noticed.
Pages:
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277