notch, between the two being of considerablè depth. From the condyle there is
j a nearly vertical line to the posterior process of the angle of the jaw, which is a
strong hook curved downwards, upwards and inwards, with â central ridge on
its inner aspect with a groove above and below it. The dental canal commences
below and slightly anterior to the condyle, and opens externally below the first
premolar.
The replacement of the deciduous by the permanent teeth I have been able
to trace in three specimens, one of which is remarkable from the circumstance that
it presents eleven teeth on one side of the upper jaw and ten on the opposite side—an
abnormality full of interest.
The first skull has all its deciduous teeth intact, except one, and yet, contrary
to what prevails among Insectívora generally in which the deciduous teeth are
shed at an early period, it is nearly the size of a full-grown cranium, and vthe individual
as a mounted specimen has all the appearance of full age. From these skulls
it would appear that Horsfield’s representations of the dentition of T. ferrugmea
and T. javcmica exhibit deciduous dentition, and that Muller and SchlegeFs figure 8,
plate 27, does the same. Professor Mivart has fully described the characters of the
grinding surface of the molars, and pointed out, what these specimens fully verify,
that the third deciduous premolar resembles the true molars, but is replaced by a
tooth of a markedly different character.
I shall describe the deciduous teeth, and indicate in passing in what respects the
permanent teeth differ from them.
Commencing with the third premolar, that tooth has three external small cusps
on a line, and resembles a molar, the central cusp showing indications of a minute
cusp at its hinder extremity, two median pointed cusps, and a large internal cusp
almost embracing the other two with a small supplementary cusp at its base on its
posterior surface. The two external fangs are long and fine, and spring from the two
internal cusps ; the inner fang is stronger and stouter than the other. The long
central cusp of the permanent premolar is wedged in between the two long external
fangs of the deciduous tooth, and by the pressure on the tooth push it outwards, even
causing it to decay.
The Second premolar consists of a long laniar-like central cusp with an
internal and a postero-extemal cusp, the last connected to the large cusp by a well-
marked ridge. The large cusp corresponds to the long median cusp of the third
deciduous premolar and to the median cusp of a molar. I t is flattened on its inner
aspect, and at its base it has the projecting ridge or inner cusp of the faintly
developed cingulum. This cusp and, the two others are fastened in the jaw by a
corresponding number of long fangs, the two outer of which are divergent.
The first premolar has two cusps ; the large anterior cusp partakes more of the
character of the head of the canine than of the large cusp of the other premolars,
and has a small posterior prolongation not nearly so high as itself, sloping off to the
gum ; each cusp is supported by a long and strong fang. There is no internal cusp,
This deciduous tooth is the first to fall out.
The milk incisor is a long tooth, more or less compressed laterally, with a crown
resembling the anterior cusp of the first premolar. The second incisor is more pointed
than the canine, but preserving to a certain extent the same character of crown.
The first incisor is cylindrical, with its crown slightly outwardly divergent, as in
Crocidura. The canine and the two incisors are curved downwards, forwards, and
backwards.
These deciduous teeth are succeeded by the permanent teeth in the following
order. The third premolar supplants its molar-like predecessor by having its large
and strong cutting edge wedged in between the outer fangs—a space which it completely
fills. The second premolar has its long cusp wedged in in a similar way
between the long, slender, external fangs of its antecedent. The large cusps of the
foregoing teeth are more external to the fangs of the deciduous teeth than equally
between or internal to them. In the first premolar, however, the permanent cusp is
internal to the fangs of the deciduous teeth rather than between them. The permanent
canine is placed right in front of the tooth it supplants, whilst this arrangement
is reversed in the case of the first and second incisors.
The third permanent premolar presents two prominent cusps, one corresponding
to the median cusps of the molars, and the other to the internal cusp of these teeth.
The cingulum is continuous along the outer surface of the base of the crown, and is
prolonged into a cusp at its anterior and posterior extremities. The large cusp
is conical and twice as large as any of the corresponding cusps of the molars : it is
convex on its internal and external surfaces, but hollowed out or deeply concave on
its postero-extemal aspect. The second premolar has not the cingulum continuous
externally, for it occurs only along the posterior half of the external surface, where
it developes a cusp nearly as large as in the preceding tooth. The cingulum is
continuous internally from the posterior to the anterior margin, and in the latter
situation it terminates in a small prominence. The central conical cusp which
forms the bulk of the tooth is nearly as large, but slightly more pointed than in
the previous tooth, and viewed internally is a little concave from above downwards,
while it is pronouncedly convex from before backwards. This tooth and the
former have three fangs, as in the deciduous teeth. The first premolar has a
conical eusp resembling those of the third and second premolars; but there is no
trace of a cingulum, and it wants the postero-extemal concavity or groove: there
are very obscure prominences on the anterior and posterior margins corresponding
to the anterior and posterior cusps of the third molar: two fangs correspond to
these prominences. The internal aspect of the tooth is markedly convex, and the
internal surface, especially near the tip, is flattened from above downwards, and
slightly concavehowever, it is strongly convex from before backwards. This is the
smallest of all the teeth, and has the least vertical extension of the premolar a.nH
incisor teeth.
The canine has a straight posterior margin, and the anterior margin is parallel
to it throughout the upper half of its extent, but below that it is bevelled off from
before backwards to the posterior margin. I t is slightly compressed from side to