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:-- [Illustration: Fig. 139. GENERALIZED SECTION OF THE TRIASSIC ROCKS OF CENTRAL EUROPE.] 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