EXTINCTION OF MAMMALS. 375 
“forest bed’ of the Norfolk coast:-differs less from the later form, occurring on the 
banks of the Lena, than does the latter from the comparatively modern mammoth 
of the superficial bogs of North America, which I regard as being only a slight 
geographical variety of the same species.” 
Tue Extinction oF Speciric Forms or MAMMALS 
From the first appearance of Proboscideans to the Recent period, one 
form after another has passed away, to be succeeded by another, until 
- we have arrived at the immediate precursor of the existing Indian ele- 
phant, which appears to be specifically identical with the mammoth. 
Falconer insists on the importance of the fact that throughout the whole 
geological history of each species of elephant there is great persistence 
in the structure and mode of growth of each of the teeth, and that this 
is the best single character by which to distinguish one species from 
another. He finds, after a critical examination of a great number of 
specimens, that in the mammoth each of the molars is subject to the same 
history and the same variation as the corresponding molar in the living 
Indian elephant.* Even if zoologists agree that these two elephants 
belong to the same species, /. primigenius is sufficiently distinguished as 
a well marked variety to deserve recognition for all the purposes of geo- 
logical description. No single cause may account for the extinction of 
the mammoth all over the world. As will be pointed out further on, it 
may have been due to the climatic changes in Siberia, while human 
agency may have been the final cause in Europe and North America; 
but whether the Indian elephant is specifically identical with FE. primi- 
genius or not, there appears to be at the present time a general tendency 
to extinction in the existing form, as one which has run its course. The 
cause of this is not apparent, unless it be owing to the well known general 
law that the higher species of animals have a shorter term of existence 
than the lower ones, and that the period of their survival is somewhat 
proportionate to their rank in the scale of being. 
The history of the larger mammals shows that when the geographical 
range of a species has become greatly diminished, with a corresponding 
reduction in its numbers, it does not recover lost ground, but hastens to 
its end. These conditions now apply to the Indian alenlham's, whether 
he represents the very circumscribed remnant of the once almost cosmo- 
politan mammoth or not. Another sign of the approaching extinction 
of this species is its loss of reproductive vigor, as evidenced by the fact 
that it will scarcely breed at all in the state of domestication. 
As the mammoth lived contemporaneously in the old and new worlds 
* Op. cit., p. 168. 
