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 affinity 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. 
