354 THE CAUSES OF THE XI 
been known in past times, and left remains 
behind. | 
Now, how many of those are absolutely extinct ? 
That is to say, how many of these orders of animals 
have lived at a former period of the world’s history 
but have at present no representatives? That is 
the sense in which I meant to use the word 
“extinct.” I mean that those animals did live 
on this earth at one time, but have left no one 
of their kind with us at the present moment. 
So that estimating the number of extinct animals 
is a sort of way of comparing the past creation as 
a whole with the present as a whole. Among the 
mammalia and birds there are none extinct; but 
when we come to the reptiles there is a most 
wonderful thing: out of the eight orders, or 
thereabouts, which you can make among reptiles, 
one-half are extinct. These diagrams of the 
plesiosaurus, the ichthyosaurus, the pterodactyle, ~ 
give you a notion of some of these extinct reptiles. 
And here is a cast of the pterodactyle and bones 
of the ichthyosaurus and the plesiosaurus, just as 
fresh-looking as if it had been recently dug up ina — 
churchyard. Thus, in the reptile class, there are 
no less than half of the orders which are absolutely : 
extinct. If we turn to the Amphibia, there was — 
one extinct order, the Labyrinthodonts, typified 
by the large salamander-like beast shown in this 
diagram. | 
No order of fishes is known to be extinct, 
POTTY RS Sree OTE! NOME) NTE OOTY wee 
