ELEPHANTS 711 



at a time on either side above and below. As they wear 

 down they are pushed forward and upward by succeeding 

 teeth behind them. In this way the teeth are continually 

 being moved forward, and pass through the jaws from be- 

 hind forward as they are worn down. No other living 

 group of mammals, with the exception of the manatees, are 

 known to possess a similar method of tooth succession. 

 The teeth usually number six on a side, the first three which 

 pass through the jaw being considered the milk molars. 

 The largest tooth of all in number of enamel plates and in 

 size is the last one to appear, the number of plates usually 

 being more than twice as many as in the first tooth. The 

 lower jaw is extremely short in the typical elephants, and 

 furnished only with molar teeth, but is armed in some of the 

 more primitive elephants, such as the mastodon, by short 

 incisor tusks. The living elephants are remarkably distinct 

 from other mammals, and until recently paleontologists 

 have not been able to trace them back to their probable 

 remote ancestral forms. Recently, in beds of Eocene age 

 at Fayum, Egypt, Doctor Andrews, of the British Museum, 

 discovered fossil remains of some ancestral forms which 

 tend to link the modern elephants with forms which show 

 some aflrinity to the ancestors of the manatees. The exami- 

 nation of the bones of these remote elephant-like mammals 

 has led Doctor Andrews to believe that Africa was the orig- 

 inal home of the elephants, and that later, during Miocene 

 time, some of the more highly developed forms spread north- 

 ward into Europe, Asia, and North America, and finally, 

 during Pleistocene time, into South America. The fossil 

 genera and species of elephants are very abundant in the 

 Pliocene and Pleistocene of Europe, Asia, and North America. 



