Humboldt discovered specimens on some of the most elevated ridges of
the Andes; and similar remains have been found in Africa. In the
frozen regions of the far North, surrounded by successive layers of
everlasting ice, the fossil ivory exists in a state of perfect
preservation, and it constitutes indeed an important article of
commerce in the north of Europe.

2. _The teeth of the hippopotamus, or river-horse_.--These, under the
inappropriate term of 'sea-horse teeth,' supply the most suitable
ivory for the dentist. In addition to twenty grinders, the animal has
twelve front teeth, the outer on each side of the jaw being the
largest and most prized. This ivory is much harder, closer in the
grain, and more valuable than that of the elephant. It is remarkable,
moreover, for the extreme hardness of its enamel, which is quite
incapable of being cut, and will strike fire with a steel instrument.
The large teeth of the hippopotamus weigh on the average 6 lbs., and
the small ones about 1 lb. each. Their value ranges from 6s. to 40s.
per lb.

3. _The teeth of the walrus, or sea-cow_.--These are nearly straight,
and measure from 2 feet to 2-1/2 feet in length. The exterior portion
of the tooth possesses a much finer grain and texture than its core,
which in appearance and properties bears a close resemblance to
ordinary bone. Of a yellowish cream-colour and mottled, this ivory is
much less valuable than the teeth of the hippopotamus. It is seldom
applied in our day to other than dental purposes; but its antiquity is
interesting. The Scandinavian relics of the eleventh and twelfth
centuries, with which our museums are so profusely enriched, are for
the most part formed of the teeth of the walrus. The elegant spiral
horn of the narwhal or sea-unicorn also produces ivory of a superior