This, the last sub-family of the _Lemuridæ_, is considered to contain the
highest members of the whole Sub-order. They are distinguished by having
their fur abundant, longer and woolly above, shorter beneath, with the
hands and feet haired to the tips of the digits. Their head, set at right
angles to the spinal column, is rounded, the face elongated and naked, with
a deep furrow separating the nostrils. The eyes are large, and have a third
eyelid, or nictitating membrane, to draw across the pupil during the day.
The ears, which are naked inside and fringed {91}on the outside, are
moderately long and buried in the fur, but are less movable at will than is
the case with the Galagos. Their fore-limbs are much shorter than the hind
ones. The arms, which are united to the body by a parachute-like fold of
integument, have long, narrow, and strong hands, of which the thumb is
short, set far back, and but little opposable. The rest of the fingers,
except the index, which is short, are long and slender, and terminate in a
round disc. The feet are elongate, and the great toe, which is freely
opposable to the other toes, is very large and broad, being, indeed, nearly
as wide as the rest of the digits together; the remaining toes are united
by a membrane as far as the second segment. The females have the mammæ
situated on the breast.
In the skull the facial region is relatively small, and the cranial region
relatively large. The external nostrils communicate with a cavity on the
underlying bone; the pre-maxillary bones are deeply excavated in front, and
the anterior perforations in the bony palate, behind the incisor teeth, are
large. The lower jaw has its angle large, produced backwards, the line of
union of its two halves being long, and its lateral movements very limited.
In regard to their dentition, the number of the milk-teeth in the young
individual is greater than that of the permanent set in the adult, the
formula of the former being I2/2, C1/1, P2/3 [M3/3], while that of the
latter is I2/2, C1/0, P2/2, M3/3, the lower canine and one lower pre-molar
having disappeared. In the upper jaw the incisors are very small, the outer
one standing behind the inner one, with a space between the former and the
canine; the canines are long, curved behind, and set close up to the
anterior pre-molar. The pre-molars are longer than they are broad,
laterally compressed, and present to the outside one main triangular cusp
with a small accessory cusp on each {92}side, the posterior tooth of the
series having a hind inner cusp. The anterior and median molars are
four-cusped, of which the outer and inner pairs are separated by a
longitudinal groove; to the outside they have one supernumerary cusp on
each main cusp, and one between them. The median molar is the largest tooth
of the jaw, and the posterior is small, triangular and three-cusped. Of the
lower jaw, the outer pair of the long, and almost horizontally protruding
incisors, is larger than the inner pair, and is separated by a space from
the anterior pre-molar. Of the elongate laterally compressed pre-molars,
the anterior is the larger, and is vertically taller than its fellows,
being slightly depressed forward and curved behind; the posterior pre-molar
has one cusp. The molars have four cusps, of which the inner ones alternate
with the outer cusps.
The intestinal canal in the _Indrisinæ_ is very long, the cæcum, or blind
diverticulum at the junction of its two portions, being extremely long and
large, occupying, indeed, a great part of the abdominal cavity. The main
arteries of the fore- and hind-limbs do not break up into a _rete
mirabile_, or series of small parallel vessels, as in many other Lemuroids.
In this group, while the sense of smell is very perfect, that of hearing is
less acute than in the other Sub-families; and that of touch conspicuously
blunt, both in the fingers and toes, which are chiefly climbing and not
tactile and prehensile organs, as they are in the corresponding limbs of
the Anthropoids. The female never produces more than one young at a birth.
The convolutions of the brain are few, but they are more complicated than
in many of the South American Monkeys. In very young individuals the
cerebellum is more covered by the cerebrum than it is in the adult.
{93}The species of this Sub-family are confined to the island of
Madagascar. Our knowledge of their general characters, anatomical structure
and habits, is very complete, through the researches, both in the field, of
M. Grandidier, and in the study, of Prof. Alphonse Milne-Edwards. These
results are published in their magnificent "Histoire de Madagascar," to
which the reader is referred for fuller information.
The _Indrisinæ_, on account of their superior organisation, and especially
their relatively large brain, are considered to be the highest of all the
Lemuroids. They are essentially arboreal. If they come to the ground they
sit upright on their hind-legs, and progress by jumps, holding their arms
above their heads. They are easily tamed, and become gentle in confinement;
but they are not very intelligent. The Endrinas "never manifest in any very
marked manner," so MM. Milne-Edwards and Grandidier tell us, "the passions
that affect the Apes so vividly; their countenance, almost as immobile as
that of an herbivorous or carnivorous animal, exhibits neither anger nor
pleasure. In captivity they do not seek to be caressed; they appear neither
to become attached to their master, nor to take interest in anything about
them." Many of their actions, however, and the peculiar sounds they often
utter, recall those of Monkeys.
Some of the species are diurnal and others nocturnal.
The Sub-family has been divided into three genera, _Avahis_ with one
species; _Propithecus_, with three species, and _Indris_ with a single
species. All its members are remarkable for the extraordinary amount of
variation in the coloration of their fur.
{94}THE AVAHI LEMURS. GENUS AVAHIS.
_Avahi_, Jourdan, C. R., Journal l'Inst., ii., no. 62, p. 231 (1834).
_Avahis_, Milne-Edwards and Grandid., Hist. Nat. Madag., Mamm., i., p.
320 (with full synonymy).
This genus is monotypic, containing but a single species, whose characters
include necessarily those of the genus.