142 
Geology of Sydney. 
Labyrinthodonts will be best understood for the general 
reader by the following tabular statement : — 
Mastodonsaurus ts 
Allied to Fishes. 
By having cup- shaped 
vertebrae. 
By breathing with 
gills in the earlier 
stages of its growth . 
The vertebrae are 
composed of three 
separate pieces, an 
arrangement pecu- 
liar to some primi- 
tive fishes. 
The infolded teeth 
connect it with 
some ganoids. 
With regard to the imprints resembling the 
impressions of human hands, and already referred to, 
it may be inquired if these are really the tracks left by 
Labyrinthodonts. 
As far back as 1834 a German geologist, Dr. Kaup, 
proposed the name Cheirotherium 1 for the great un- 
known animal that left the footprints. As Sir R. Owen 
points out, the impressions of the Cheirotherium 
resemble the footprints of a modern salamander in 
having the short outer toe of the hind foot projecting 
Allied to Reptiles. 
■Itwas acold-blooded 
vertebrate that 
breathed by lungs, 
and lived mostly 
on the land. 
It had a bony skele- 
ton with well- 
developed ribs. 
Differs from 
Reptiles. 
By having two con- 
dyles, and by 
breathing by gills 
when young. 
The whole of the 
upper portion of 
the skull is roofed 
in by a single bone. 
I Greek — Cheir , hand ; therion , beast. 
