64 THE ORIGIN OF MAN 



peds and the armored quadrupeds, while from the 

 latter arose a third, the horned dinosaurs or Cera- 

 topsia. Of these three types, the unarmored Or- 

 nithopoda, or bird-footed dinosaurs depended for 

 defense largely upon fleetness of foot. As they 

 had a powerful compressed tail and their hands 

 had a webbed character, they had the swimming 

 powers of an alligator and still retained the abil- 

 ity to travel rapidly on land. When therefore 

 they were hard pressed by the carnivores they 

 could easily take to the water if they were unable 

 to escape the onslaught by speed ashore. But 

 all herbivorous dinosaurs were not of this de- 

 fenseless type. The second race, the Stegosauria, 

 or armored dinosaurs, had their bodies encased in 

 an almost impregnable armor. Later the armor 

 became more and more massive, the bony ele- 

 ments being welded into a broad protective shield 

 or carapace covering the creature's back, while 

 the heavily armored tail was like a huge battle 

 mace. A most remarkable feature of Stego- 



