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OF THE GRINDERS. 81
first Bimspis was of the same shape and size as a Grinder, and
projected, for want of room, between the Cuspidatus and second
Bicuspis. These and the Grinders alter very little in shape on
their grinding surfaces by use; their points only wear down, and
become obtuse.
OF THE GRINDERS.
In describing the Grinders (o) we shall first consider the first
and second conjunctly, because they are nearly the same in
every particular; and then give an account of the third or
last Grinder, which diners from them in so;ne circumstances.
The two first Grinders differ from the Bicuspides, principally
in being much larger, and in having more points upon their
body, and more fangs.
(o) [The following is a brief sketch, of some of the more striking
modifications presented by the molar and premolar series in the Mam-
It has been compiled from the previously-quoted work
malian orders.
of Professor Owen.
In the order Bruta, the teeth for the most part belong to the molar
series. The characteristics of the dentition in this order are, that each
tooth is implanted by an undivided base, the implanted portion con-
tinuing of the same thickness as the crown. In no species of this
order possessing teeth are these organs implanted by divided roots, or is
there a cervix separating the crown of the tooth from the implanted
The base is excavated for the entrance of a persistent pulp, and
part.
the tooth continues to grow throughout life. The teeth are devoid of
In the Cape Ant-eater (Orycteropus Capensis), the
a coating of enamel.
. The two
teeth all belong to the molar series. Its dental formula is£: £;
anterior teeth in the upper jaw, and the anterior tooth in the lower jaw,
are very small, and not unfrequently concealed by the gum, or wanting,
especially the first, in the upper jaw. The tooth in front of the penul-
timate, and the penultimate are the largest. These two teeth have
a depression on their internal and external sides, which gives their
transverse section somewhat of an bour-glass form, each tooth is im-
planted by a truncated undivided base. The tooth of the Orycteropus
consists of long, slender, prismatic denticles of dentine cemented
together ; the base of each denticle presents the conical opening of
These openings give a porous character to the
a persistent pulp cavity.
The aperture at the base of each denticle
base of the entire tooth.
leads to a canal from whence the dentinal tubules radiate. The denti-
cles are united laterally by cement ; they slightly decrease in diameter,
and occasionally bifurcate as they approach the grinding surface of the