150 THE TIME OF THE MAMMOTHS. 
with the long intervals of repose between them. During the 
middle and later tertiary periods elephantine life had its 
highest development; a half a dozen or more species lived 
then on the surface of the European continent, and only a 
portion of the then existing forms may be known to us. 
The importance of the elephant life of this time may be 
better estimated by comparing the number of large mammals 
belonging to any one family now existing in the same area. 
Only three or four species of the family of cervide, to which 
the common deer belongs, have existed in Europe since the 
glacial period. Among the bulls not more than two.species 
are known to have lived during the same time. Nor among 
the large carnivora, the bears or wolves, have the species 
been more numerous. We must seek among the smaller of the 
existing mammals, among the squirrels or mice, for the same 
riehness in specific representation as we find among the ele- 
phants of the tertiaries. The variety in size and form seems 
to have been very great; the smallest species was not over 
three or four feet high, while the largest stood as high as 
any of our living elephants, towering to the height of ten or 
twelve feet. We know too little of the geology of the other 
continents of the old world to say whether this exceeding 
richness in large elephants at this stage of the earth's history 
was also found there. We know, however, that India, 
where one of the two remaining species of elephants lives, 
was thronged with these animals at this time, and although 
Africa was probably then separated from the other continents 
with which it is now closely united by seas of considerable 
width, it, too, probably bore an abundance of the same life. 
We do not know the character of the life of the middle ter- 
tiary time in North America with anything like the accuracy 
that we do that of Europe during the same time. The in- 
vestigations which are to enable us to form a clearly defined 
picture of the life of that time, on our own continent, are yet 
to be made. It seems likely, however, that during the time 
when elephants were so remarkable a feature in the life 
