FAUNA OF THE TRIAS. 73 
the Cheirotheria, or Labyrinthodonta (colossal Batra- 
chians) possess pre-eminently amphibian characters, and 
exhibit, for example, several important characteristics of 
the Batrachian skull, whereas their skin-covering recalls 
the scale-armour of the Saurians. Thus we find cha- 
racters combined which are subsequently divided among 
different groups. There are also traces of huge sea-lizards. 
But here, and likewise in the magnesian limestone for- 
mation, these amphibian-like animals still keep in the 
background amid the profusion of Ganoids, which espe- 
cially characterizes some of the strata of the magnesian 
limestone formation, the Kupferschiefer, or cupriferous 
marl formation. For the sake of classification, the Zech- 
stein is not unfitly supposed to conclude a great period 
of organic development: the series of formations from 
the Silurian to the end of the Zechstein is termed palz- 
azoic ; and those which follow, the Trias, Oolite, and 
Cretaceous formations, are summed up as mesozoic. 
The Trilobites, the mailed Ganoids, and others have 
now disappeared, and the enormous development of 
reptile life stamps this middle period. The Trias as 
yet possesses no true Teleostei. The Labyrinthodonta 
still predominate; while the Archzosauros and the Pro- 
terosaurus, which had already appeared in the Dyas, are 
replaced by more numerous forms approximating to the 
true reptiles. One single discovery in the upper member 
of the Trias—the teeth of a predatory marsupial—has 
supplied us with the most ancient traces of a mammal. 
It might be inferred, even from the petrographic cha- 
racter of the oolitic strata, that this era must have been, 
on the whole, far more favourable to the development of 
animal life than the more perturbed Triassic period, or 
