erches sur les Poissons Fossiles.' Agassiz.
(17) 'Ichnology of Annandale.' Sir William Jardine.
(18) 'Die Fossile Flora der Permischen Formation.' Goeppert.
(19) 'Genera et Species Plantarum Fossilium.' Unger.
(20) "On the Red Rocks of England of older Date than the Trias"
--'Quart. Journ. Geol. Soc.,' vol. xxvii. Ramsay.

CHAPTER XV.

THE TRIASSIC PERIOD.

We come now to the consideration of the great _Mesozoic_, or
Secondary series of formations, consisting, in ascending order,
of the Triassic, Jurassic, and Cretaceous systems. The Triassic
group forms the base of the Mesozoic series, and corresponds
with the higher portion of the New Red Sandstone of the older
geologists. Like the Permian rocks, and as implied by its name,
the _Trias_ admits of a subdivision into three groups--a Lower,
Middle, and Upper Trias. Of these sub-divisions the middle one
is wanting in Britain; and all have received German names, being
more largely and typically developed in Germany than in any other
country. Thus, the Lower Trias is known as the _Bunter Sandstein_;
the Middle Trias is called the _Muschelkalk_; and the Upper Trias
is known as the _Keuper_.

I. The lowest division of the Trias is known as the _Bunter
Sandstein_ (the _Gres bigarre_ of the French), from the generally
variegated colours of the beds which compose it (German, _bunt_,
variegated). The Bunter Sandstein of the continent of Europe
consists of red and white sandstones, with red clays, and thin
limestones, the whole attaining a thickness of about 1500 feet.
The term "marl" is very generally employed to designate the clays
of the Lower and Upper Trias; but the term is inappropriate, as
they may contain no lime, and are therefore not always genuine
marls. In Britain the Bunter Sandstein consists of red and mottled
sandstones, with unconsolidated conglomerates, or "pebble-beds,"
the whole having a thickness of 1000 to 2000 feet. The Bunter
Sandstein, as a rule, is very barren of fossils.

II. The Middle Trias is not developed in Britain, but it is largely
developed in Germany, where it constitutes what is known as the
_Muschelkalk_ (Germ. _Muschel_, mussel; _kalk_, limestone), from
the abundance of fossil shells which it contains. The Muschelkalk
(the _Calcaire coquillier_ of the French) consists of compact
grey or yellowish limestones, sometimes dolomitic, and including
occasional beds of gypsum and rock-salt.

III. The Upper Trias, or _Keuper_ (the _