THE GREAT FISH-LIZARDS. 
49 
two; and no doubt our fish-lizard would have been glad to 
perform the same feat ! But in his pre-Adamite days the oppor- 
tunity did not present itself. 
The spinal column, or backbone, with its generally concave 
vertebrse, must have been highly flexible, as is that of a fish, 
especially the long tail which the creature worked rapidly from 
side to side as it lashed the waters. 
The hollows of these concave vertebrae must have been 
originally filled up with fluid forming an elastic bag, or capsule. 
To get a clearer idea of this, take a small portion of the back- 
bone of a boiled cod, or other “bony” fish, and you will 
see on pulling it to pieces, the white, jelly-like substance that 
fills up the hollows between the vertebrae. In this way Nature 
provides a soft cushion between the joints, that allows of 
a certain amount of movement, while, at the same time, the 
column holds together. The backbone of a fish may not 
inaptly be compared to a railway train. Each of the carriages 
represents a vertebra, and the bufiers act as cushions when the 
train is bent in running round a curve. After all, we must 
learn from Nature ; and many of the greatest mechanical and 
engineering triumphs of to-day are based upon the methods 
used by Nature in the building up and equipment of vegetable 
and animal forms of life. 
It may, perhaps, be inquired whether there is any evidence for 
the existence of a tail-fin, such as is shown in our illustration. 
To this it may be replied that the presence of such an appendage 
is as good as proved by a certain flattening of the vertebrae 
at the end of the tail, detected by Owen. The direction of 
this flattening is from side to side, and therefore the tail-fin 
must have been vertical, like that of a fish. In one specimen 
Sir Richard Owen has detected as many as 156 vertebrae to 
the whole body. 
Our description of the fish-lizard has, we trust, been sufficient — 
E 
