Under this family heading are included the whole of the remaining members
of the Sub-order. They all possess certain main characters in common; but
on account of the presence or {23}absence of certain subordinate features
in some of the groups, the family has been further subdivided into four
sub-families. The more important characters which they have in common are
the thick woolly fur, the Dog- or Fox-like snout and nostrils--a character
obviously distinguishing them from the bulk of the Monkeys, in which the
nose forms a subsidiary feature, and is not the main part of the face,--and
especially the number and form of their teeth. In the centre of the upper
jaw there is always a toothless gap, or _diastema_, on each side of which
the teeth are arranged according to the following formula: I2/2, C1/1,
P3/3, M3/3 = 36. Among the Endrinas, however, the formula is I2/2, C1/(1 or
0), P2/2, M3/3 = 32 or 30 in number. In the upper jaw the incisors are
small and perpendicular; but in the lower, where they are long and narrow,
they protrude horizontally in front, and then follow, parallel and close to
them, the somewhat thicker canines, the six teeth together forming a
comb-like series. The anterior pre-molar is always vertically longer than
the others, and assumes the form and function of the canines in other
animals.
In some genera (e.g., _Propithecus_), Milne-Edwards has observed that in
the young animal the cerebellum is more overlapped by the cerebrum (or main
brain) than it is later in life; and Dr. Major believes that the _Lemuridæ_
are highly specialised members of the Sub-order, developed from ancient
types which were not unlike the American Monkeys of the family _Cebidæ_.
The Typical Lemurs are arranged in the following four sub-divisions: The
Pottos and Slow-paced Lemurs (_Lorisinæ_); the Galagos and Mouse-Lemurs
(_Galaginæ_); the True Lemurs (_Lemurinæ_); and the Endrinas (_Indrisinæ_).
{24}THE SLOW-LEMURS. SUB-FAMILY I. LORISINÆ.
This Sub-family has been constituted to receive a small number of Lemurs,
which, although occupying limited areas in two widely separated
continents--one genus being African and the others Asiatic--present certain
characters in common. They are recognised by having soft woolly fur, a
triangular head and pointed face, very large and staring eyes, set close
together, while their ears are naked along their margin. Their fore- and
hind-limbs are nearly equal. In the Asiatic genera the index finger is very
small, while in the African it is quite rudimentary and nail-less. In both
groups the thumb diverges widely from the other fingers, and the great toe
is directed backwards, but the ankle-bones of the foot are not elongated.
The tail is either so short as to be quite concealed in the fur, or is less
than one-third of the length of the body.
[Illustration: Fig. 6. Front Teeth of Perodicticus, Nycticebus and Loris,
after Mivart (P. Z. S., 1864, p. 631).]
In the skull the squamosal region with the outer and posterior portion of
the ear capsules (the periotic) are inflated. The dental formula of the
Slow-Lemurs is the same as given above for the family generally. In the
upper jaw, the two incisors are usually equal, but, if unequal, the inner
incisor is always the larger (Fig. 6); the vertically long canine, which is
separated by a gap from the anterior pre-molar, presents both in front and
behind a neck or cingulum, which is cusped behind; the pre-molars are
canine-like, and have the cingulum produced behind into a heel (or talon).
The anterior of the three is {25}vertically longer than the median, while
both the median and posterior have, to the outside, one main cusp with a
minute one on each side of it, and two inner cusps; the molars are all
cingulate, and have to the outside two main cusps (separated by a minute
cusp) and two inner cusps, the outer and inner cusps alternating. Of the
anterior and median molars, the two main outside cusps are sub-equal, and
are flanked on each side by a minute cusp; the posterior molar is short and
wide, and has only one minute cusp in front of its anterior main cusp. Of
the lower jaw, the pre-molars are canine-like, the anterior being
vertically long and having a posterior heel; the posterior pre-molar, which
differs in size from the anterior, presents two main cusps to the outside
and one minute cusp in front; the molars, both anterior and median, are
four-cusped, with a minute cusp in front, the posterior being five-cusped,
while all have their front cusps vertically taller than the hind ones.
Among the _Lorisinæ_ the dorsal and lumbar vertebræ together number from
twenty-one to twenty-three. The cæcum, at the junction of the larger and
smaller intestine, is long. The main artery of the fore- and hind-limbs
breaks up into a _rete mirabile_ of numerous small parallel branches.
The Slow-Lemurs are distributed in the western parts of the African
continent, and in the Indian, Malayan and Indo-Chinese portions of the
Oriental region. It is a remarkable fact that this group should be confined
to one portion of Africa and be entirely absent from Madagascar, the
country where the Lemurs form so characteristic a feature in the fauna.
The _Lorisinæ_ embrace three genera, the Pottos (_Perodicticus_) from the
African continent; the Slender Loris (_Loris_), and the Slow-Loris
(_Nycticebus_), both of which inhabit the Oriental region.
{26}THE POTTOS. GENUS PERODICTICUS.
_Perodicticus_, Bennett, P. Z. S., 1839, p. 109; Huxley, P. Z. S., 1864,
p. 235.
_Arctocebus_, Gray, P. Z. S., 1863, p. 150; Mivart, P.Z.S., 1864, p. 644.
This genus contains two species, both confined to the West Coast of Africa.
The Pottos are slender-bodied animals, with oval heads and blunt Dog-shaped
muzzles. Their eyes are large and full, and their external ears erect, with
shelf-like lamellæ inside. They have slender and sub-equal limbs. The
second digit of the fore-limb is rudimentary and nail-less; it is supported
on one wrist-bone, and has two phalanges or finger-bones. The great toe is
opposable, and the fourth and fifth digits of both limbs are united
together by membrane as far as the first joint. The processes of the
vertebræ in the neck and back are long and protruding. The tail is very
short.
The pre-maxillæ (which carry the incisor teeth) do not project in front,
nor does the bony palate extend farther back than the end of the posterior
molar teeth. Of the upper teeth the incisors are equal in size (Fig. 6);
the median and posterior pre-molars have on their crowns three cusps, of
which the two outer are the larger; the anterior and median molars are
cingulate, have four-cusped crowns, and are larger than the pre-molars; the
posterior is narrow from before backwards, and its crown presents only two
or three cusps. Of the lower teeth, the anterior pre-molar is recurved and
larger than the canine, with a ridge on its inner face and a cusped heel
behind; the median and posterior ones are shorter than their anterior
fellow, each having a strong posterior cusped heel; the anterior and median
{27}molars have their crowns four-cusped and are nearly equal in length;
the crown of the posterior molar is 4-5-cusped, and has a ridge joining its
anterior heel to its front outer cusp. Transverse and oblique ridges are
well marked on the crowns of both the upper and lower cheek-teeth.