like were these impressions
to the shape of the human hand, that the at that time unknown
animal which produced them was at once christened _Cheirotherium_,
or "Hand-beast." Further discoveries, however, soon showed that
the footprints of _Cheirotherium_ were really produced by species
of Amphibians which, like the existing Frogs, possessed hind-feet
of a much larger size than the fore-feet, and to which the name
of _Labyrinthodonts_ was applied in consequence of the complex
microscopic structure of the teeth (fig. 149). In the essential
details of their structure, the Triassic Labyrinthodonts did not
differ materially from their predecessors in the Coal-measures
and Permian rocks. They possessed the same frog-like skulls (fig.
150), with a lizard-like body, a long tail, and comparatively
feeble limbs. The hind-limbs were stronger and longer than the
fore-limbs, and the lower surface of the body was protected by an
armour of bony plates. Some of the Triassic Labyrinthodonts must
have attained dimensions utterly unapproached amongst existing
Amphibians, the skull of _Labyrinthodon Joegeri_ (fig. 150) being
upwards of three feet in length and two feet in breadth. Restorations
of some of these extraordinary creatures have been attempted in
the guise of colossal Frogs; but they must in reality have more
closely resembled huge Newts.

Remains of _Reptiles_ are very abundant in Triassic deposits,
and belong to very varied types. The most marked feature, in
fact, connected with the Vertebrate fauna of the Trias, and of
the Secondary rocks in general, is the great abundance of Reptilian
life. Hence the Secondary period is often spoken of as the "Age
of Reptiles." Many of the Triassic reptiles depart widely in
their structure from any with which we are acquainted as existing
on the earth at the present day, and it is only possible here to
briefly note some of the more important of these ancient forms.
Amongst the group of the Lizards (_Lacertilia_), represented by
_Protorosaurus_ in the older Permian strata, three types more
or less certainly referable to this order may be mentioned. One
of these is a small reptile which was found many years ago in
sandstones near Elgin, in Scotland, and which excited special
interest at the time in consequence of the fact that the strata
in question were believed to belong to the Old Red Sandstone
formation. It is, however, now certain that the Elgin sandstones
which contain _Telerpeton Elgi