The remains of Cycads, as we have seen, are not known to occur
in the Coal formation, or only to a very limited extent towards
its close; nor are they known with certainty as occurring in
Permian deposits. In the Triassic period, however, the remains
of Cycads belonging to such genera as _Pterophyllum_ (fig. 141,
b), _Zamites_, and _Podozamites_ (fig. 141, c), are sufficiently
abundant to constitute quite a marked feature in the vegetation;
and they continue to be abundantly represented throughout the
whole Mesozoic series. The name "Age of Cycads," as applied to
the Secondary epoch, is therefore, from a botanical point of
view, an extremely appropriate one. The _Conifers_ of the Trias
are not uncommon, the principal form being _Veltzia_ (fig. 141,
a), which possesses some peculiar characters, but would appear
to be most nearly related to the recent Cypresses.
[Illustration: Fig. 141.--Triassic Conifers and Cycads. a, _Voltzia_
(_Schizoneura_) _heterophylla_, portion of a branch, Europe and
America; b, Part of the frond of _Pterophyllum Joegeri_, Europe;
c, Part of the frond of _Podozamites lanceolatus_, America.]
As regards the _Invertebrate animals_ of the Trias, our knowledge
is still principally derived from the calcareous beds which
constitute the centre of the system (the Muschelkalk) on the
continent of Europe, and from the St Cassain and Rhaetic beds
still higher in the series; whilst some of the Triassic strata
of California and Nevada have likewise yielded numerous remains
of marine Invertebrates.
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