8 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



a lucky cast of the lead might some day bring up from 

 the depths of the seas as had already happened in 

 the case of the Pentacrinum and the Trigonia but 

 with genera and even families of terrestrial mammals 

 entirely different from the existing mammals. 

 The zoological exploration of our continents was 

 complete enough for Cuvier to be able to affirm the 

 unlikelihood of any further discoveries of great 

 living mammals. This presumption has been other- 

 wise verified, with a few rare exceptions, of which 

 the most striking have been the discoveries of the 

 rhinoceros of Java, the white-backed tapir of 

 Sumatra, and quite recently the Okapi of the 

 great African equatorial forest. 



Not only do the sedimentary layers of the earth's 

 surface contain genera and species of extinct animals, 

 but these vanished populations have been several 

 times renewed. This important conclusion was 

 suggested to Cuvier by the study of the innumerable 

 materials sent by scholars in all countries to the 

 illustrious specialist, as well as by numerous visits 

 to the lands and geological collections of Germany, 

 Belgium, Switzerland, and Italy. After the very 

 remarkable epoch of the gypsum of Montmartre, 

 nearly all the genera of which have vanished, 

 came the epoch* of the deposit of alluvial soils, in 

 which predominate the mastodon, the hippopotamus, 

 and the elephant, accompanied by the horse, by 

 various ruminants, and the great carnivora of like 

 stature with the lion, the tiger, and the hyena. But 

 it is a remarkable fact that although most of these 

 genera have continued to exist in our present 

 world, their species, at least, are entirely distinct 



