Fossils. 
141 
connection can there be between the Tucttara lizard 
and the extinct Labyrinthodonts that pottered round 
the ancient swamps, which in Triassic times spread out 
where Sydney now stands ? In Fig. 84 we have repro- 
duced the skull of a Lahyrinthooont. A little forward 
from the base of the skull, and behind the eye cavities, 
a small round hole may be seen, just over the brain 
cavity. It represents the site of a small third eye. 
Now, on studying living animals, we find that the 
little Tuatara lizard of New Zealand has a small 
aperture similarly situated, and overlying the rudi- 
ments of an eye. The ancestors of the Tuatara lizard 
no doubt made use of this third eye, and it is 
extremely probable the Labyrinthodonts made a like 
use of a third eye. So it comes to pass that the 
Tuatara lizard throws some light upon the use of that 
aperture in the ancient Labyrinthodont. 
As is well known, the vertebrae of the backbones 
of fishes have hollow articulating surfaces. A single 
vertebra of a fish will be found cupped-shaped on 
both surfaces. Indeed, this is one of the characters of 
the backbone of all fishes. The backbone of Labyrin- 
thodont has similar cupped-shaped vertebrae. So 
we have here a certain connecting link with fishes. 
\\ e have said enough now to show the interesting 
position of the extraordinary creatures we are describ- 
ing. Quite sufficient to bear out the contention that 
they are really connecting links between the two well- 
defined classes of fishes and reptiles. The affinities of 
