retained. He suspects that the Shrews have but one dentition : the
minute size and rudimental state of the transitory teeth, and their
disappearance before birth having caused them to escape the observation
of the accomplished continuator of Cuvier’s “ Leçons d’Anato-
mie Comparée.” (1)
C H A P T E R V I I I .
TEETH OF CHEIROPTERA.
165. T h e dental system presents more constancy in this than in
the preceding Order, and the different kinds of teeth are more easily
and unequivocally determinable.
The canines are always present in both jaws, of the normal form
and with slightly variable proportions. The molar series never
exceeds JjEf, and is divisible into premolars and true molars, the latter
presenting two types of grinding surface ; in one of these the crowns
are bristled with sharp points, as in the foregoing order, and this type
characterizes the great bulk of the Cheiroptera, which may be called
true Bats or volant Insectivores ; the molars of the second type have
flat crowns and characterize the large frugivorous Bats which constitute
the aberrant genus Pteropus, and conduct towards the Quadru-
manous Order.
The incisors are the most variable teeth in the Cheiroptera ;
(1) See the posthumous edition of the Leçons, tom. iv, p. 242, where M. Duvernoy adds
to the text : “ J’ai lieu de penser que tous les Insectivores n’ont pas cette succession de dents.
Je l’ai constatée, à la vérité, dans les Tenrecs. qui perdent leurs dents fort tard, au contraire
de certains Rongeurs les ayant trouvées encore, en partie, chez un individu dont la taille
était à peu près celle de l’adulte. M. Laurillard l'a vue dans les Chauve-souris et les Hérissons.
Mais dans les Musaraignes je suis porté à croire qu'il n'y a qu'une seule dentition." M. de
Blainville goes further, and denies the existence of a deciduous series of teeth in the Mole,
Hedgehog and Tenrec, (Ostéographie des Insectivores, p. 63) ; as, indeed, he likewise did with
regard to the Bats, (Compte Rendu de l'Académie des Sciences, Sept. 1837, p. 420.) M.
Rousseau, in his excellent “ Mémoire sur la Chauve-souris commune," read to the Academy
of Sciences, March 19th, 1838, described the deciduous dentition of that Cheiropter with all
the requisite detail, and its existence is admitted by M. de Blainville in the “ Ostéographie des
Chéiroptères," published in June 1840. Similar proofs will be found, if nature be rightly
consulted, that the other Insectivora, also, form no exception to the rule.
they may be entirely wanting, or be present in the numbers of
1—1 to 2—2 in the upper, and from 1—1 to 3—3 in the lower
jaw ; they are always very small, and in the upper jaw commonly
unequal and separated by a wide median vacancy. Taking the
common simple-nosed Bat(l) (Vespertilio-murinus) as a type of the
Insectivorous group, we find its dental formula to be :—
i.n . 2—^-2 : c. —1—1 : pm. —3—8 : m. 3——8 : = 3«. 3—8 / 1—1 ’ r 3—3 j 3—3
The first upper incisor (PL 112. fig. 1 ,i.) has a slightly expanded
tri-dentate crown, separated by a basal ridge of enamel from a long,
slender, slightly curved, fusiform fang ; the second upper incisor
has a sub-bifid crown. The three lower incisors (i) are tri-dentate,
and the crown of the outermost has an additional tubercle.
The crown of both upper and lower canines (c c) is sharp-
pointed, and its inner surface is indented by two grooves; a basal
ridge divides it from the long conical fang. The first premolar is
very small, both above and below, and has a sharp-pointed simple
crown with a basal ridge, and a single fang; the second premolar
is still smaller: both are soon shed. The third premolar, as it may be
called from its shape, though it has no deciduous predecessor, has a
triangular pointed crown, with a basal ridge, and is implanted above by
three fangs ; in the lower jaw the crown is narrower, and is supported
by two fangs (p p). The first and second upper true molars (m), have
each a six-pointed crown supported by three fangs : the third molar
is compressed from before backwards; its crown has three points or
tubercles, and is supported by three fangs. The first and second
true molars of the lower jaw have quinque-cuspid crowns, two of
the largest points being on the outer and three small ones on the
inner side, the crown is supported by two fangs ; the last molar
is the smallest, and is tri-cuspid. A well-developed ridge of enamel
surrounds the base of the crown of each molar tooth both above and
below.
(1) The insectivorous Cheiroptera are divisible into groups according to the modifications
of the tactile dermal appendages of the nose ; which may be wanting, as in the Vespertilio mur-
inus and other Leionyderides ; or be present in the form of a simple leaf, as in the Vampire-bat
and other Phyllonycteridce; or he developed into more complex forms, as in the Horse-shoe
Bat and other Lophonyderidce of Prof, de Blainville.