182 THE STORY OF REPTILE LIFE. 



which reference has been made, proceeded simul- 

 taneously with that of the carnivorous, and it 

 would appear attained even more striking results 

 in the matter of bulk, some species having reached 

 a quite colossal size. 



In the course of their evolution many changes, 

 other than mere increase in size, are to be 

 remarked. Thus in some we find more or fewer 

 of the teeth suppressed, and their place taken 

 by horny plates ; in others, we meet with the 

 development of heavy armour, intended to serve 

 the purposes either of offence or defence. Again, 

 it is to be noted that bipedal and quadrupedal 

 forms alike competed in the race for size, and 

 though in the end victory rested with the 

 quadruped types the race was keen and close. 



The huge beast known as Brontosaurus excelcus 

 from the Jurassic of Colorado may be taken as 

 a type of the quadrupedal group. Attaining a 

 length of between 50 and 60 feet, this creature 

 was remarkable for the small size of its skull, 

 which was smaller in proportion to the size of 

 its body than in any other known Reptile. The 

 jaws were armed with blunt-pointed teeth. The 

 neck and tail were of great length, whilst the 

 trunk was comparatively short. The weight of 

 such an enormous body was greatly reduced by 

 the hollo wn ess of the bones, which were, through- 

 out the skeleton, permeated by large air cavities. 

 In another closely allied contemporary, Diplodocus 

 longus, we see the effect of specialisation in regard 

 to feeding habits reflected in the dentition, which 

 was of a very curious type. Only the front of 

 the jaws bore teeth, and these were extremely 



