XIV 



A RETROSPECT 



The twenty years that have elapsed since this book was 

 issued have added much to our knowledge of Animals of 

 the Past and have greatly increased our acquaintance 

 with the structure of these creatures, big and Uttle, and 

 of the conditions under which they lived. And through 

 our increased knowledge of animals, we gain a better 

 knowledge of ancient geography, of the former extent 

 of the continents and of the way in which the present 

 distribution of land animals has been brought about. 



Exploration of the desert region of the Fayum, north- 

 eastern Africa, has led to the discovery of the ancestor 

 of the elephant; and as the horse is descended from a 

 four-toed ancestor no bigger than a collie dog, so the 

 elephant, and his extinct gigantic relatives, the mam- 

 moth and mastodon, probably trace their pedigree back 

 to a creature in size and appearance something between 

 a pig and a tapir, with only good-sized canine teeth to 

 suggest the future appearance of tusks: Moeritherium 

 this animal has been called. In this same region lived a 

 race of huge animals, curiously suggestive of the Ti- 

 tanotheres of our western Miocene. Here, too, have 

 been found the forerunners of our modern sea cows, 

 manatees and dugongs, very much like their modern 

 relatives, but possessing — as theoretically they should — 

 hind paddles as well as fore. 



The additions to our knowledge of those huge and 

 ever-interesting reptiles, the Dinosaurs, have been 

 many and important. 



From the Cretaceous of Alberta comes Ankylosaurus 

 clad in armor of bony plates from tip of nose to end of 

 tail, a beast some 15 feet long aptly described by Lull 

 as "the most ponderous animated citadel the world has 



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