556 THE UNIVERSE. 



mals with such skill that, in spite of the destruction of the 

 softer organs thousands of years ago, they have been ena- 

 bled to make out the structure of the intestinal tube ! It 

 has been shown that this was formed exactly like an Archi- 

 median screw, and was strictly analogous to that of our 

 sharks and rays. At the same time the nature of the food 

 of these voracious rep f iles has been discovered. These two 

 facts were revealed by an examination of the faeces or cop- 

 rolites of Ichthyosauri, which are found in large quanti- 

 ties in some localities. Their form, moulded on that of the 

 intestine, showed the structure quite clearly ; while the 

 petrified remains of food which were discovered proved that 

 these animals devoured an enormous quantity of fish, and 

 even occasionally their own species ; for small Ichthyosauri 

 have been met with in the bellies of the large ones. 



With these terrible dominators of the Jurassic seas lived 

 the Plesiosauri, reptiles equally strange, and which Cuvier 

 considered as the most abnormal races of the ancient world. 

 They were remarkable for their turtle-like fins, and es- 

 pecially for the thinness and extreme length of their ser- 

 pent-like necks. The arrangement of the skeleton in the 

 Plesiosaurus led Mr. Conybeare to think that it swam or- 

 dinarily on the surface of the waves, curving back its long 

 flexible neck like a swan, and darting forward with it from 

 time to time in order to seize the fish which approached it. 

 Their paws, analogous to those of the sea-turtles, induced 

 this learned Englishman to think also that the Plesiosauri, 

 like these reptiles, sometimes issued from the sea, and sought 

 refuge amid the plants, in order to evade their dangerous 

 enemies, which were beyond all doubt the Ichthyosauri. 



