_Hapalemur_, Is. Geoffr., Cat. Méth. Primates, p. 74 (1851).
This genus has been constituted for two species of a specialised type of
Lemur, characterised by a globose head, a short muzzle, with a tapering
nose and short hairy ears. The hind-limbs are longer than the fore-limbs,
the feet short and broad, and the tail hairy and equal in length to the
body. The female has four teats, two on the breast, or on the shoulder, and
two on the abdomen.
In regard to their skeletal characters, the facial portion of the skull is
short and narrow in front--the nasal bones being arched--and the brain-case
rounded. The cranium presents no elevated frontal crests, as among the
members of the next genus (_Lepidolemur_). The pre-maxillary bones are very
small. The hind margin of the bony palate, which dilates posteriorly, does
not extend behind the mid-line of the last molar. The squamosal region of
the skull and the outer and posterior--the mastoidal--portion of the
ear-capsules (periotic bones), is not inflated in the members of this
genus. Their lower jaw is very characteristic, being massive in front and
possessing a very long symphysis (or line of junction of its two halves),
its angle being {80}also very large, and produced downward, inward, and
backward, even more than in the genus _Indris_. The _naviculare_ bone of
the ankle (_tarsus_) is relatively short, thus differing from the same
region in _Microcebus_ and in _Galago_; the _carpus_ (or wrist) has no
central (_os centrale_) bone.
In _Hapalemur_ the teeth are of the normal Lemurine number, viz., 36; but
the dentition as a whole is peculiar and characteristic. Each series of
teeth is very uniform and equal, and those anterior to the molars are
serrated. In the upper jaw the incisors are very small, sub-equal, and
situated close together; the posterior tooth on each side being (when the
skull is viewed from the side) internal to and touching the canines. The
canines are small, and the gap between them and the anterior pre-molar is
very small. The anterior pre-molar is slightly taller vertically than its
median fellow, and stands close up to it without an interval; it has one
main (and sometimes one rudimentary) outer cusp; the posterior pre-molar,
which closely resembles a molar, and is often the largest tooth in the jaw,
having one inner cusp united by ridges to its two outer cusps. The molar
teeth are sub-equal to the hindmost pre-molar, and have one front inner and
two outer cusps, without an oblique ridge between them, and also a
well-developed cingulum, cusped externally. Of the lower teeth, the
anterior and median pre-molars are set obliquely, the median having three
outer and two inner cusps (the two inner being united to the two hind outer
by ridges). The posterior pre-molar is quite molariform, and, with the
molars, presents three outer and two (or three) inner cusps, of which the
two inner are united by ridges to the outer hind cusps, while transverse
ridges unite the main outer and inner cusps together. The molars are
cingulate towards the outside.