prints, 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
and the Rhaetic or Koessen 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 m