594 



HISTORICAL GEOLOGY 



It is interesting to speculate on the causes of the extinction of this 

 race which may have had an existence of more than a million years. 

 Its fate may have been due to two causes : (i) to the small size of 

 the brain, and (2) to the poorness of the grinding teeth which were 

 no more efficient in the huge forms towards the close of the period 

 than in the earlier and smaller species. The low brain power was 

 of disadvantage to them in their competition with other forms and 

 also gave them little ability to protect their young from the more 

 crafty carnivores. Bulk is a disadvantage under changing conditions 

 (p. 550) and may alone have been responsible for the disappearance 

 of the race. This great order was one of the many which, for a 

 time, took a prominent place among the animals of the world, but 

 which after a long span of life disappeared, leaving no descendants. 



REFERENCES FOR AMBLYPODA 



Chamberlin and Salisbury, — Geology, Vol. 3, pp. 232-233. 

 Hutchinson, H. N., — Extinct Monsters and Creatures of Other Days, pp. 249-260. 

 Scott, W. B., — A History of Land Mammals in the Western Hemisphere, pp. 443-451. 

 Woodward, A. S., — Vertebrate Paleontology, pp. 292-299. 



Ancestors of the Carnivores. — The earliest Eocene carnivores 

 (Creodonta) are so generalized {i.e., combine characters now possessed 



Fig. 537- — A primitive carnivorous mammal, creodont (Middle Eocene). 

 (After Professor Osborn.) 



by widely different groups of animals) that it is difficult to tell even 

 to what order they belong. Their teeth are rather better adapted 

 for cutting food than for grinding it (none, however, have sectile 

 teeth, perfectly adapted for flesh eating) ; and their toes are provided 

 with curved nails that are rather clawlike but are not the sharp, 

 retractile claws such as are possessed by the cat to-day. These 

 creatures were descended from others whose feet were even more 



