J30 FOSSIL MAMMALIA. 
rivers. To an animal of such habits, the weigh* 
of the tusks sustained in water would have been 
no source of inconvenience ; and, if we suppose 
them to have been employed, as instruments fo* 
raking and grubbing up by the roots large 
aquatic vegetables from the bottom, they would- 
under such service, combine the mechanic^ 
powers of the pick-axe with those of the horse- 
harrow of modern husbandry. The weight o 
the head, placed above these downward tusks, 
would add to their efficiency for the service here 
supposed, as the power of the harrow is increase 
by being loaded with weights. 
The tusks of the Dinotherium may also have 
been applied with mechanical advantage to hoo 
on the head of the animal to the bank, with the 
nostrils sustained above the water, so as 
breathe securely during sleep, whilst the body 
remained floating, at perfect ease, beneat* 
the surface : the animal might thus repose, 
moored to the margin of a lake or rive 
without the slightest muscular exertion, the 
weight of the head and body tending to fix an ^ 
keep the tusks fast anchored in the substance e 
the bank; as the weight of the body of a sleep 
ing bird keeps the claws clasped firmly aroun 
its perch. These tusks might have been furthe* 
used, like those in the upper jaw of the 
rus, to assist in dragging the body out of 
water; and also as formidable instruments ^ 
defence. 
