1.Koessen beds.
(Synonyms, Upper St Cassian beds of Escher and Merian.
 Grey and black limestone, with calcareous marls having a thickness of about 50 feet. Among the fossils, Brachiopoda very numerous; some few species common to the genuine Lias; many peculiar. Avicula contorta, Pecten Valoniensis, Cardium Rhœticum, Avicula inœquivalvis, Spirifer Münsteri, Dav. Strata containing the above fossils alternate with the Dachstein beds, lying next below.
2.Dachstein beds.
 White or greyish limestone, often in beds three or four feet thick. Total thickness of the formation above 2000 feet. Upper part fossiliferous, with some strata composed of corals (Lithodendron.) Lower portion without fossils. Among the characteristic shells are Hemicardium Wulfeni, Megalodon triqueler, and other large bivalves.
3.Hallstadt beds
(or St Cassian)
 Red, pink, or white marbles, from 800 to 1000 feet in thickness, containing more than 800 species of marine fossils, for the most part mollusca. Many species of Orthoceras. True Ammonites, besides Ceratites and Goniatites, Belemnites (rare), Porcellia, Pleurotomania, Trochus, Monotis salinaria, &c.
4.A.Guttenstein beds.
B.Werfen beds, base of Upper Trias?
Lower Trias of some geologists.
A.Black and grey limestone 150 feet thick, alternating with the underlying Werfen beds.
B.Red and green shale and sandstone, with salt and gypsum.
 Among the fossils are Ceratites cassianus, Myacites fassaensis, Naticella costata, &c.

In the United States, rocks of Triassic age occur in several areas between the Appalachians and the Atlantic seaboard; but they show no such triple division as in Germany, and their exact place in the system is uncertain. The rocks of these areas consist of red sandstones, sometimes shaly or conglomeratic, occasionally with beds of impure limestone. Other more extensive areas where Triassic rocks appear at the surface, are found west of the Mississippi, on the slopes of the Rocky Mountains, where the beds consist of sandstones and gypsiferous marls. The American Trias is chiefly remarkable for having yielded the remains of a small Marsupial (Dromatherium), and numerous footprints, which have generally been referred to Birds (Brontozoum), along with the tracks of undoubted Reptiles (Otozoum, Anisopus, &c.)

The subjoined section (fig. 139) expresses, in a diagrammatic manner, the general sequence of the Triassic rocks when fully developed, as, for example, in the Bavarian Alps:—

GENERALIZED SECTION OF THE TRIASSIC ROCKS OF CENTRAL EUROPE.
Fig. 139.

With regard to the life of the Triassic period, we have to notice a difference as concerns the different members of the group similar to that which has been already mentioned in connection with the Permian formation. The arenaceous deposits of the series, namely, resemble those of the Permian, not only in being commonly red or variegated in their colour, but also in their conspicuous paucity of organic remains. They for the most part are either wholly unfossiliferous, or they contain the remains of plants or the bones of reptiles, such as may easily have been drifted from some neighbouring shore. The few fossils which may be considered as properly belonging to these deposits are chiefly Crustaceans (Estheria) or Fishes, which may well have lived in the waters of estuaries or vast inland seas. We may therefore conclude, with considerable probability, that the barren sandy and marly accumulations of the Bunter Sandstein and Lower Keuper were not laid down in an open sea, but are probably brackish-water deposits, formed in estuaries or land-locked bodies of salt water. This at any rate would appear to be the case as regards these members of the series as developed in Britain and in their typical areas on the continent of Europe; and the origin of most of the North American Trias would appear to be much the same. Whether this view be correct or not, it is certain that the beds in question were laid down in shallow water, and in the immediate vicinity of land, as shown by the numerous drifted plants which they contain and the common occurrence in them of the footprints of air-breathing animals (Birds, Reptiles, and Amphibians). On the other hand, the middle and highest members of the Trias are largely calcareous, and are replete with the remains of undoubted marine animals. There cannot, therefore, be the smallest doubt but that the Muschelkalk and the Rhætic or Kössen beds were slowly accumulated in an open sea, of at least a moderate depth; and they have preserved for us a very considerable selection from the marine fauna of the Triassic period.

The plants of the Trias are, on the whole, as distinctively Mesozoic in their aspect as those of the Permian are Palæozoic. In spite, therefore, of the great difficulty which is experienced in effecting a satisfactory stratigraphical separation between the Permian and the Trias, we have in this fact a proof that the two formations were divided by an interval of time sufficient to allow of enormous changes in the terrestrial vegetation of the world. The Lepidodendroids, Asterophyllites, and Annulariœ, of the Coal and Permian formations, have now apparently wholly disappeared: and the Triassic flora consists mainly of Ferns, Cycads, and Conifers, of which only the two last need special notice. The Cycads (fig. 140) are true exogenous plants, which in general form and habit of growth present considerable

Fig. 140.—Zamia spiralis, a living Cycad. Australia. resemblance to young Palms, but which in reality are most nearly related to the Pines and Firs (Coniferœ). The trunk is unbranched, often much shortened, and bears a crown of feathery pinnate fronds. The leaves are usually "circinate"—they unroll in expanding, like the fronds of ferns. The seeds are not protected by a seed-vessel, but are borne upon the edge of altered leaves, or are 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.

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 Rhætic beds still higher in the series; whilst some of the Triassic strata