carried on the scales of a cone.  All the living species of Cycads are natives of warm countries, such as South America, the West Indies, Japan, Australia, Southern Asia, and South Africa.  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.  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.