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OF THE GRINDERS. 83
two of which are on the inner, and three on the outer part of
the Tooth ; and generally some smaller points at the roots of
these larger protuberances. These protuberances make an irre-
gular cavity in the middle of the Tooth. The three outer points

ramus—and shorter than in the male. The smallest teeth are those at
each extremity of the series. They are implanted by fangs, and are
lodged in a wide and moderately-deep groove in the jaw, which is
sockets, the septa reaching only about half
imperfectly divided into
way from tbe bottom of the groove. The intervals separating these
teeth are about as broad as themselves. The sockets are too wide and
too shallow to retain the teeth independently of the soft parts ; hence,
in the dried condition, when the ligamentous gum is stripped off, it
often happens that the whole row of teeth is brought away with it.
These teeth, when the mouth is closed, enter depressions in the upper
gum. A few rudimentary primitive teeth (representing those which
even in the true "Whales (Balcenidce), are always present in the jaws in
the foetal condition) are retained in the upper gum in the Cachalot.
They are more curved than the functional teeth in the lower jaw. In
the young Cachalot, the tooth is tipped with enamel, but after a time
the apex becomes worn down, and the tooth consists of a hollow cone
of dentine coated by cement, and filled more or less with ossified pulp.
In the Dolphins teeth are present in both jaws ; they vary considerably
in number in different species. The teeth are generally conical, strong,
and pointed, and implanted by a single fang, but more firmly than in
the Cachalot. In most Dolphins, the anterior teeth become obtuse by
the wearing down of their sharp apices ; whilst the posterior teeth con-
tinue sharp-pointed ; the usual position of piercing and bruising teeth
being thereby reversed. An exception to this, however, is presented by
the Gangetic Dolphin (Platanista gangetica). In it the anterior teeth
retain their prehensile characters, whilst the crowns of the posterior
become worn away to the base. Professor Owen has noticed that
sometimes the base of the posterior tooth in the Gangetic Dolphin, is
divided into two short fangs, a conformation probably unique in existing
carnivorous Cetacea. A large extinct animal, which, from the cha-
racters and microscopic structure of its teeth, Professor Owen believes
to have been a Mammal, allied to the Cetaceans, and which he has
named Zeuglodon, or yoke-tooth, had its posterior teeth implanted by
The crown of the posterior tooth in the Zeuglodon is
double fangs.
contracted from side to side in the middle of its base, so as to give its
transverse section an hour-glass form ; and the deep longitudinal
opposite grooves which produce this form become deeper and deeper as
they approach the socket, and at length unite to divide the root into
two fangs. The upper part of the crown has its anterior and posterior
margins strongly serrated. The anterior teeth of the Zeuglodon have