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 

 vertebrae, 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 buffers 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 



