_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. The _Protozoans_ are represented by
_Foraminifera_ and _Sponges_, and the _Coelenterates_ by a small
number of _Corals_; but these require no special notice. It may be
mentioned, however, that the great Palaeozoic group of the _Rugose_
corals has no known representative here, its place being taken
by corals of Secondary type (such as _Montlivaltia, Synastoea_,
&c.)

The _Echinoderms_ are represented principally by _Crinoids_,
the remains of which are extremely abundant in some of the
limestones. The best-known species is the famous "Lily-Encrinite"
(_Encrinus liliiformis_, fig. 142), which is characteristic of the
Muschelkalk. In this beautiful species, the flower-like head is
supported upon a rounded stem, the joints of which are elaborately
articulated with one another; and the fringed arms are composed
each of a double series of alternating calcareous pieces. The
Palaeozoic Urchins, with their supernumerary rows of plates, the
Cystideans, and the Pentremites have finally disappeared; but
both Star-fishes and Brittle-stars continue to be represented.
One of the latter--namely, the _Aspidura loricata_ of Goldfuss
(fig. 143)--is highly characteristic of the Muschelkalk.

[Illustration: Fig. 142.--Head and upper part of the column of
_Encrinus liliiformis_. The lower figure shows the articulating
surface of one of the joints of the column. Muschelkalk, Germany.]

[Illustration: Fig. 143.--_Aspidura loricata_, a Triassic Ophiuroid.
Muschelkalk, Germany.]

The remains of _Articulate Animals_ are not very abundant in the
Trias, if we except the bivalved cases of the little Water-fleas
(_Ostracoda_), which are occasionally very plentiful. There are
also many species of the horny, concentrically-striated valves
of the _Estherioe_ (see fig. 122, b), which might easily be
taken for small Bivalve Molluscs. The "Long-tailed" Decapods
of the t