86 EXTINCT MONSTERS 
do, regard the metamorphosis of the tadpole into a frog as a kind 
of object-lesson on the part of Dame Nature, given with a view 
to show us, in a general way and in a short space of time, how 
the wonderful change from the fish to the reptile took place. 
By the time the great coal-forests of the Carboniferous period 
were flourishing, the fish class had attained a high state of 
development, and were to some extent foreshadowing the 
amphibian type of creation. Now, we know that when the 
New Red Sandstone was being laid down, the next great class, 
viz. the reptiles, had not only made a start, but had struck out 
in several lines, and were specialised in certain directions, as 
shown by their bird-like footprints on the Triassic sandstones. 
Would it not therefore be expected that we should find, in rocks 
of greater age than the New Red Sandstone, the remains of 
animals in some respects intermediate between fishes and 
reptiles? This expectation is fully realised by the presence 
in such strata (i.e. the coal-measures and Permian rocks) of the 
remains of quite a large number of amphibia. They also crop 
up again in the Trias, but after that period are not much in 
evidence until we come to Tertiary times. 
The amphibian class, at the present day, is represented by 
the frogs, toads, and newts of our own country, and by the 
salamanders of Japan and the United States. But these are 
only a meagre remnant of a large number of families that lived 
ages ago. 
Let us endeavour now to take a general view of the amphibian 
class as it was in the days of long ago, before the creation of 
man,—to look at their family tree and see what their ancestors 
were like. When this is done we shall perhaps have a little 
more respect for the frogs and newts that inhabit our ponds; 
for they come of a very ancient stock, and one which played 
