EVOLUTION OF TUSKS AND TRUNK 
side branch) the lower tusks are enlarged, while the upper ones disappear. 
In Trilophodon, in the direct line of descent, the upper tusks become larger, 
the lower ones smaller, 
while the grinding teeth 
are reduced in number 
but increased in size, 
and their cross ridges 
are increased in number 
and height. In masto- 
don the lower tusks are 
rudimentary or absent, 
while the upper ones 
are of huge size, and 
the length of the trunk 
and form of the head 
approaches that of the 
modern elephant. In 
the mammoth, and in 
the existing elephants, 
no trace is left of the 
lower tusks, the upper 
ones are of enormous 
size, and the grinders, 
of great size and. per- 
fection, are reduced to 
one, on each side of 
each jaw in the adult. 
This series exhibits a 
steady increase in the 
length of the trunk, 
TRILOPHODON ANGUSTIDENS. 
A primitive mastodon, found fossil in the Middle 
Miocene strata of the south of France. “ Its ‘trunk’ 
must have rested horizontally on the lower jaw be- 
tween the upper tusks —and was, in fact, not a 
‘trunk’ at all, but an elongated upper lip — represent- 
ing the middle part of the upper jaw in a soft, flexible 
condition. It seemed to me probable that the 
elephant’s trunk had originated in this way; namely, 
by the great elongation, in the first place, of the lower 
jaw and upper lip and jaw, and by the subsequent 
shrinking of the lower jaw, and ‘ bull-dogging’ of the 
bones of the face. Thus the elongated mid-part of 
the face — no longer supported bya long lower jaw — 
would gradually drop as the lower jaw grew shorter 
and shorter in successive ages, and at last it would 
hang down as a perpendicular trunk. ... It is very 
difficult to form a definite idea as to how the Tri- 
lophodon made use .of his tusks and _ horizontal 
‘trunk.’ The upper tusks have a sharp edge along 
the inner face, strengthened by enamel, so that it is 
probable that, working against the tough skin pads of 
the lower jaw, they would serve for cutting vegetable 
matter.” — LANKESTER.187 
and the height and massiveness of the animal, and a corresponding 
lengthening of the trunk to enable the creature to reach the ground. 
The two existing kinds of elephants illustrate the difference 
between the Eastern and the Western types. 
phant is a creature of the dense forests and swampy 
grass jungles of Ceylon, eastern India, and the 
This is the one the world has known longest 
Malay region. 
The Indian ele- 
Indian 
Elephant. 
and most familiarly, and from which it has derived most of 
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