WHEN THE WORLD WAS YOUNG 187 



banks of Siberian rivers, the stupid, awkward animals 

 should have been unable to place themselves in safety, 

 and got swallowed up in the mud of the lake. 



Then, too, but much later in date, the great pampas 

 or plains of South America were the home of the ances- 

 tors of the Sloth tribe — Megatheria by name — animals 

 eighteen feet in length, whose bones are found in the 

 river deposits. As in aU animals that can, stand on their 

 hind legs, the lower limbs and back were immensely 

 strong, while the thick tail acted as ballast ; the very thigh 

 bone is three times as thick as that of an elephant. Like 

 the modern Sloth, the Megatherium had no teeth in front, 

 but it probably possessed a long and flexible tongue, which 

 it used to curl round branches of trees and tear them down. 

 It was also able to dig its sharp, powerful claws into the 

 trunk of a tree, and with a mighty heave of its body to 

 loosen the roots, and by repeating this process three or four 

 times the tree would fall to the ground, and the particular 

 morsel on which the Megatherium had set its heart would 

 be within its reach. 



Further back still we find that birds and mammals 

 have not yet come into being, but, instead, their places 

 are taken by a strange kind of flying reptile, whose wings 

 were more like those of a bat than a bird, and often 

 measured twenty-five feet. The name of Pterodactyl 

 has been given to this extraordinary creature, which 

 resembles some of the queer fancies men used to carve 

 on churches rather than anything we ever see now. The 

 pterodactyl had teeth, but no feathers, and could swim as 

 well as fly. As to its food, we guess from its teeth that 

 it lived chiefly upon fish, though it may sometimes have 

 swooped down, when flying, on little animals, or even 

 have pecked at fruit. 



But besides the pterodactyls, there existed at the same 

 period, which has been called the Age of the Eeptiles, 

 vast swarms of creatures whose forms seemed to be made 

 up of a large number of other species. In many ways 



