the dentition is modified in analogical conformity with the
Rodent type, to which, in the present instance, it makes a very close
approximation, the canines being absent and a wide vacancy separating
the single pair of large curved scalpriform incisors in each
jaw from the short series of molars.(1)
The upper incisors are compressed, presenting a narrow oval
transverse section, with the long diameter from before backwards ;
they are curved in the segment of a circle, and deeply implanted ;
the short exserted crowns touch one another ; their simple, widely
excavated fangs diverging as they penetrate the substance of the
jaw. The short crowns project obliquely forwards and do not
extend vertically downwards as in the true Rodentia.
The lower incisors are more compressed, and of greater
breadth from before backwards, than the upper ones ; they are
more curved than in the Rodentia, describing a semicircle, two
thirds of which are lodged in the socket, which extends backwards
beyond the last molar tooth to the base of the coronoid.
The anterior edge of the oblique cutting surface does not rest
against a posterior ridge of the surface of the tooth above,
whence M. de Blainville infers that these large scalpriform
teeth were put to a different use from that to which the same
teeth of the Rodents are habitually applied. He conjectures,
that they served the Cheiromys rather as a pair of cutting
pincers to remove the bark and perhaps the wood of trees in
search of larvae or insects, which, however, the smooth, flat
crowns of the molars would not indicate to have been the staple
food of the Cheiromys. The most important character by which
the incisors of this anomalous Lemur differ from those of the
Rodentia is the entire investment of enamel, which is, however,
thicker upon the front than upon the hack part of the
tooth.T
he molar teeth are four on each side of the upper jaw, 1
(1) PI. 114, fig. 2. M. de Blainyille, who first pointed out the affinity of the Cheiromys
to the Quadrumana, has made the observation that the edentulous margin of the jaw between
the ineisors and molars is sharp, as if it had lodged some small teeth that had been shed;
whilst in the true Rodentia it is always broadly rounded off and smooth.
and three on each side of the lower jaw, implanted vertically
and in parallel lines. (1) The molars are of simple structure,
with a continuous outer coat of enamel, and a flat sub-
elliptic grinding surface: the upper ones are of unequal size,
the first being the smallest, and the second the largest: in the
lower jaw the inequality is less, and the last molar is the least.
The first and last molars above have but one root: the second
and third have each three roots. The first lower molar has two
roots, the second and third have each a single root.
169. Lemuridcc.—The Indris (Lichanotus, Uliger) are small tail-less
Lemurs, which, when full-grown, have but two incisors in the lower
jaw, of larger size than in other Lemurs, especially in the species
{Lich. Diadema) on which the sub-genus Propithecus has been founded.
The dental formula in the Lichanotus Indri and Lich. lanigtr, is :—
Incisors ^ ; canines ; premolars ; molars : == 30.
In the common Indri the upper incisors, especially the anterior
one, are proportionally larger than in the higher Lemuridas, in
the woolly Indri (PI. 114, fig. 6) they are very small. In both
species the canine has a trihedral straight compressed conical crown;
the premolars have shorter compressed crowns : the first and second
molars have square, four-lobed crowns; the last molar is triangular
and of smaller size. The lower canine (c) is directed obliquely
forwards parallel with the incisor, which it closely resembles in
the Lichanotus laniger; in the common Indri it is longer and
larger. The premolar and molar teeth resemble those above, but
the last supports five tubercles.
The dentition of the Malmags or Spectre-Lemurs (Tarsiusj
offers a more insectivorous character;(2) the formula is:—
T . Incisors 2——2 ; cani. nes 1——1 : premo,l ars 3——3 : mo,l ars 3——3 : = 31 4. 1—1 * 1—1 ’ r &-3 ’ 3—3
The first upper incisor, as in the Shrews, is longer than the canine.
The inferior canines (c) are characterised, as in other Lemuridcc,
(1) In the general characters of the teeth of the Rodentia, p. 400, the convergence of the
molar series is noticed.
(2) PI. 114, fig. 3.