PTEROSAURS 47 1 



appearance these reptiles much resembled the modern Gavial of 

 India and had a similar elongate and slender snout. The fore 

 legs were much smaller than the hind, and these animals were 

 doubtless of more exclusively aquatic habit than the crocodiles 

 and alligators of the present day. 



The Dinosauria have become much larger, more numerous and 

 diversified than they had been in the Trias, though, as the foot- 

 prints in the Newark sandstones teach us, only a small fraction of 

 the Triassic Dinosaurs has yet been recovered. Making all due 

 allowance for this, it seems, nevertheless, to be true that the group 

 had made notable progress in the Jurassic. The group of Dino- 

 sauria is a heterogeneous one, comprising reptiles of very different 

 size, appearance, structure, and habits of life. Some were heavy, 

 slow- moving quadrupeds, having fore and hind legs of not very 

 unequal length, with hoof-like toes, and usually with very small 

 heads. Dinosaurs of this type were mostly plant-feeders and had 

 rows of grinding teeth adapted for such a diet. Cetiosaurus is an 

 example of this kind of Dinosaur, which attained a length of 40 

 feet. Scelidosaurus is another herbivorous reptile, but with such 

 short fore legs that the gait must have been bipedal, or else the 

 back must have been arched upward very strongly to the hind 

 quarters. This animal, and its ally, Omosaurus, were provided 

 with an armour of bony plates and spines covering the back and 

 tail. Megalosaurus, on the other hand, was a gigantic carnivorous 

 Dinosaur, having terrible, sharp-pointed teeth, while the toes were 

 armed with sharp, curved claws. These creatures walked upon 

 their elongated hind legs and were the most formidable beasts of 

 prey that scourged the Jurassic lands. Not all of the Jurassic 

 Dinosaurs were gigantic ; very small ones also ranged through the 

 forests or may even have been arboreal in their habits. Compso- 

 gnathns, for example, was a bipedal, carnivorous Dinosaur hardly 

 larger than a house cat. 



Another very remarkable order of reptiles, the Pterosauria, 

 appears for the first time in the Jurassic (Fig. 157). These ani- 

 mals were provided with wings, and were true fliers, thus realizing 

 the old myth of flying dragons. The head is relatively large, but 



