Triassic life is entirely different from anything that had preceded it, though the way for the change was already preparing in the Permian. As we have seen, the Upper Permian, if classified by its plants alone, would be referred to the Mesozoic rather than to the Palaeozoic, and we are therefore prepared to learn that the Triassic flora is very similar to that of the Upper Permian, though the Upper Trias, especially the Rhaetic, marks a decided advance among the plants. Among the animals a considerable number of surviving Palaeozoic types persist into the Trias which do not pass into the Jurassic.

Plants

Triassic vegetation is composed of Ferns, Horsetails, Cycads, and Conifers, and of such plants were the Newark coal of Virginia and North Carolina, the Keuper coal of Germany and Sweden, and the Triassic coal of South Africa and Australia accumulated. The Ferns are relatively somewhat less abundant than they had been in the Carboniferous, and many of them belong to the existing tropical family of the Marattiacece. Tceniopteris, Caulopteris, Cla-thropteris, are among the most important genera. In Virginia a magnificent fern with very broad leaves, Macrotceni-opteris (Fig. 283), is the most abundant and characteristic of the Triassic plants there found.

The Lycopods have undergone a great reduction since the Carboniferous, though a few straggling specimens of plants related to Sigillaria, but belonging 10 a distinct family, have been found in the Lower Trias. The Cal-amites are no longer found, but on the other hand, true Horsetails of the modern genus Equise-tum now make their first appearance, and much surpass their modern representatives in size, having stems of 4 inches in thickness. Rhizomes and stems of these plants are very common, and dense growths of them, like cane-brakes, surrounded the inland seas and salt lakes of the period. The Cordaitece have disappeared, but the Cycadales with their stiff leaves abounded, growing, doubtless, on the dryer lowlands above the swamps, most of them belonging to such genera as Pterophyllum, Zamiks, and Otoza-mites (Fig. 284). This group of plants is a characteristic Mesozoic one, and the era is sometimes called the "Age of Cycads." The term Cycaddies is employed to indicate "a group enormously wider than our recent Cycadaceae." (D. H. Scott.) The Gingkoaceae continue to be represented by Baiera. On the hills and uplands grew dense forests of Conifers, in appearance like the Araucarians, which are found to-day in South America, Polynesia, and Australia. Araucarites, and the cypress-like Voltzia (Fig. 285), the latter much resembling the Permian Walchia, are common genera.

While the Triassic flora is thus different from that of the Palaeozoic, it must have given to the landscapes of the period much the same appearance of graceful and luxuriant, but somewhat gloomy and monotonous, vegetation. Probably the fern forests of New Zealand give the best modern picture of these early Mesozoic woodlands.

A Triassic Fern, MacrotcBni opteris magnifolia Rogers. Restored (Russell).

Fig. 283. - A Triassic Fern, MacrotcBni-opteris magnifolia Rogers. Restored (Russell).

Triassic Conifer, Voltzia heterophylla.

Fig. 285. - Triassic Conifer, Voltzia heterophylla.

(Fraas).

Leaf of a Triassic Cycad, Otozamites latior Saporta, X 1/2. (Newberry).

Fig. 284. - Leaf of a Triassic Cycad, Otozamites latior Saporta, X 1/2. (Newberry).

Of marine plants, the Calcareous Algce, or Coralline Seaweeds, should be mentioned as very abundant about the coral reefs, to which they contributed largely.

Among the animals the change from Palaeozoic times is much more complete than among the plants.

Coelenterata

Corals abounded in the seas, wherever conditions were favourable to their growth, but the Palaeozoic Tetra-coralla have nearly died out, though a few of the Tetracoralla and of the Tabulate Hexacoralla survived. Their place is taken by the modern type Hexacoralla, though the two groups of corals approach each other so closely that the distinction is not a sharp one.

Echinodermata

In this type a more marked change has taken place. The Cystoids and Blastoids have disappeared, and the Crinoids have undergone a change of structure, the Camerata giving way to the Articulata, but the latter occur only in small numbers and in character rather transitional from the older forms than typical of the new. Of the Triassic Crinoids much the commonest is Encrinus, which is so characteristic of the German Muschelkalk. Similarly, the ancient type of the sea-urchins, the Palceechinoidea, is all but gone, only a few persisting through the Mesozoic, while the Euechinoidea, which began in a small way in the Carboniferous, now come to the front. The Triassic Echinoids are all of regular shape, the irregular forms not appear-ing till later.

Arthropoda

The long-tailed Decapod Crustacea, Macrura, are found in the Trias, probably the most ancient representatives of the group. The Ostracoda are not uncommon. The little genus of Phyllopoda, Estheria, is very common in the German Keuper and the American Newark, and seems to be indicative of brackish-water conditions where it occurs. Among the Insects, the Coleoptera (Beetles) are added to the two orders which are definitely known to occur in the Palaeozoic.

The Bryozoa undergo a marked change in the disappearance of the ancient Fenestella-like genera.

Brachiopoda

One of the most important changes from the Palaeozoic to the Mesozoic consists in the great reduction of the Brachiopods in variety and numbers, and in a difference of character, the shells with long, straight hinge-line giving way to those with short, curved hinge, like Terebratula (PI. XIII, Fig. 7). Even in the Trias the reduction is very marked, though several Palaeozoic genera have their latest representatives in the rocks of this system; as examples, may be mentioned Productus, Athyris, and Cyrtina. Koninckina is a new genus of the Spirifer family, which is confined to the Trias. The still existing genera, Terebratula and Rhynchonella, are much the most abundant brachiopods of the period, and Thecidium, which later becomes important, has its beginning here.

Mollusca

Almost in proportion to the decline of the brachiopods is the rise of the Pelecypoda, or Bivalves, which now become far more varied and abundant than they had been in the Palaeozoic. Pecten, Pseudomonotis (XIII, 8), Myophoria, Halobia, Dao-nella (XIII, 9), and Cardita, may be selected as a few examples of the commoner genera. The higher forms of the class are, however, still rare. The Gastropoda are yet in a transition stage. Several genera, such as Murchisonia, Loxonema, etc., here make their last appearance, and mingled with them are the forerunners and earliest representatives of modern types, such as Cerithium and other genera, in which the mouth of the shell is no longer a complete ring, but is drawn out into a grooved siphon.

The Cephalopoda, and more particularly the Ammonoids, have already acquired a wonderful degree of abundance and variety. The ancient Nautiloid genus Orthoceras, which ranges through almost the whole Palaeozoic group, persists into theTriassic system, but not later, and numerous coiled Nautiloids with angulated and ornamented shells recall those of the Carboniferous. Of the Ammonoids some still have the comparatively simple sutures of the Goniatites, others, like Ceratites, have slightly serrated sutures, while in the upper Triassic occur some shells in which the complexity of the sutures is carried farther than in any other known members of the group. Only a few of this great assemblage of genera can be mentioned; especially characteristic of the Trias are: Tirolites, Trachyceras, Meekoceras (XIII, 2), Arcestes, Ceratites, Tropites (XIII, 1), Joannites (XIII, 5), Gytnnotoceras (XIII, 3), Sagenites (XIII, 4), and Analcites (XIII, 6). It is very interesting to observe that in the Trias occur, though but rarely, certain unusual forms of Ammonoid shells, which do not become important until the long subsequent time of the Cretaceous period. Rhabdoceras has a straight shell, Cochloceras one that is coiled in a high spiral like a gastropod, and in Choristoceras the coils are open.

The similar Cretaceous genera were not derived from these Triassic anticipations, but are degenerate members of many Ammonoid families. The Dibranchiate Cephalopods, and especially the characteristic Mesozoic group of the Belemnites, have their earliest and most primitive representatives in the Triassic genera Atractites and Aulacoceras.

Plate XIII.   Triassic Invertebrate Fossils.

Plate XIII. - Triassic Invertebrate Fossils.

Figs, i, ia, Tropites subbullatus Hauer, side and end views, X 1/2, Up Tr. z, 2a, Meek-oceras gracilitatis White, side & front views, Low. Tr. 3, 3a, Gymnotoceras blakei Gabb, X 1/2, side and front views, Mid. Tr. 3b, The same, a suture line, x 1. 4, Sagenites herbichi Mojs. x 1/2, U. Tr. 4a, The same, a suture line, X 1. 5, 5a, Joan-nites nevadanus Hyatt & Smith, X 1/2, side and front views, M. Tr. 5b, The same, a suture line, x 1. 6, 6a, Analcites meekt Mojs. X 1/2, side and back views, M. Tr. 7, 7a, Terebrat-ula semisimplex White, X 1, dorsal and side views, L. Tr. 8, Pseudomonotis subcir-cularis Gabb, x 1/2, M. Tr. 9, Daonella lommeli Wissmann, x 1/2, U. Tr.

The Vertebrata

The Vertebrata are of extraordinary interest, and if the Trias had yielded only vertebrate fossils, it would still be apparent that great progress had been made since the time of the latest known Palaeozoic beds. The Fishes display this progress least of all the Vertebrates. Shark teeth are known, but not skeletons. The Dipnoan Ceratodus is very characteristic, continuing up from the Permian. The Crossopterygians have greatly declined, but some very large and curious fishes of this group, like Diplurus (Fig. 286), still linger. The Ganoids continue to be the dominant fish-type, especially of the inland waters, and are most like the existing garpikes. Catopterus and Ischypterus are representative American genera, and Semionotus, Dictyopyge, and Lepidotus are nearly allied European fishes.

The Amphibia reach their culminating importance in the Trias, the Stegocephalia multiplying and diversifying in a wonderful fashion, and far surpassing the genera of the Carboniferous and Permian in size. These Amphibians have been found in North America, southern Africa, and Europe; but those of the last-named continent are much the best understood, because best preserved, the Bunter sandstone of Germany being a treasure-house of such remains. Mastodonsaurus, Cyclotosaurus, and Labyrinthodon are common European genera, but there are many others. Cheirotherium (also European) is known only from its curious footprints, like the print of a human hand.