Fig. 451.   Side view of the skull of a Lemuroid (Nycticebus or Stenops tardigradus).

Fig. 451. - Side-view of the skull of a Lemuroid (Nycticebus or Stenops tardigradus).

(After Giebel.)

The largest and most important of the families of the Strep-sirhina is that of the Lemuridae or Lemurs. In this family the muzzle is elongated, the feet are all furnished with opposable thumbs, and the nails on all the toes are flat, with the exception of the second toe of the hind-foot, in which there is a long and pointed claw. The body is covered with a soft fur, and the tail is usually of considerable length, and is covered with hair. They are easily domesticated; and though capable of biting pretty severely, their disposition is gentle and docile. They are mostly about the size of cats, and not unlike them in appearance, being often termed "Madagascar cats" by sailors. They are found almost exclusively in the great forests of Madagascar, moving about amongst the trees with great activity, by means of their prehensile tails. They appear to fill in Madagascar the place occupied by the higher Quadrumana upon the adjoining continent of Africa. One of the best-known species is the Indri (Indris laniger) which occurs, with other species of the genus, in Madagascar. The genus Lemur itself includes the so-called "Makis," the most familiar of which is the Ring-tailed Lemur (Z. catta). The dental formula is:

i

2 - 2

; c

1 - 1

; pm

3 - 3

; m

3 - 3

-

36.

2 - 2

1 - 1

3 - 3

3 - 3

The "Galagos" (Galago), sometimes raised to the rank of a distinct family, are the only members of the Lemuridae which occur out of Madagascar, and they are confined to Africa, being most abundant in the western part of this continent, but one species extending its range to Senegal and the southern borders of the Sahara. All have long bushy tails, large eyes, and large membranous ears.

Platyrhina.

The section of the Platyrhine Monkeys is exclusively confined to South America, and one of its leading characters is to be found in the very general possession of a prehensile tail; this being an adaptive character by which they are suited to the arboreal life which so many of the South American Mammals are forced to lead. There are neither cheek-pouches nor natal callosities, and there is an additional praemolar, and sometimes a molar less than in Man and the Old World Monkeys. The nostrils are simple, separated by a wide septum, and opening laterally. The praemolars are in number and have blunt tubercles. The thumbs of the forehands are either wanting altogether, or, if present, are but slightly opposable, though versatile.

3 - 3

3 - 3

The Platyrhine Monkeys are divided into the two principal sections of the Hapalidae and Cebidae.

Fam. 1. Hapalidae (Arctopitheci). - In this family the number of teeth is the same as in the Old World Monkeys and in Man, but there is an additional praemolar on each side of each jaw, and a molar less. The dental formula of the Marmoset is:

i

2 - 2

; c

1 - 1

; pm

3 - 3

; m

2 - 2

-

32.

2 - 2

1 - 1

3 - 3

2 - 2

The molars, however, are tuberculate, and though the number of teeth is the same as in the Catarhine Monkeys, in their other characters, the Marmosets are genuine Platyrhines. The hind-feet have an opposable hallux with a flat nail, but all the other toes are unguiculate, and the pollex is not at all opposable. The tail is long and thickly haired, but is not prehensile.

The Hapalidae are all small monkeys, mostly about as big as Squirrels, and they are exclusively South American, occurring especially in Brazil. The best-known species is the common Marmoset (Hapale penicillata), but several species are domesticated and kept as pets. The genus Midas comprises small Monkeys which differ from the Marmosets chiefly as regards their dentition.

Fam. 2. Cebidae. - In this family are all the typical Platyrhine Monkeys, in which the dentition differs from that of the Hapalidae, in having an additional molar, so that the molars are the same as in the Catarhina and in Man, but the praemolars are more numerous. The dental formula is:

i

2 - 2

; c

1 - 1

; pm

3 - 3

; m

3 - 3

=

36.

2 - 2

1 - 1

3 - 3

3 - 3

There are neither cheek-pouches nor "callosities;" and the face is usually more or less naked, though sometimes whiskered. The tail is long, and is mostly prehensile ; though in rare instances it is non-prehensile, and has its extremity clothed with hairs. The thumb of the fore-hand may be wanting, and, if present, is not opposable. All the fingers are furnished with flat nails. Their diet is miscellaneous, consisting partly of insects and partly of fruit.

The Cebidae are exclusively confined to the warmer parts of South America, in the vast forests of which they are met with in large troops, climbing amongst the trees. The Spider Monkeys (Ateles), the Howling Monkeys (Mycetes), the "Sapa-jous" or "Capuchins" (Cebus), and the Squirrel Monkey (Callithrix), may serve as typical examples of this section of the Quadrumana. In Ateles the tail is long, slender, and powerfully prehensile; and the limbs are very long and slender. The pollex is absent, or is quite rudimentary. In Mycetes there is a bony drum which is formed by a convexity of the os hyoides and communicates with the larynx. The voice is thus rendered extraordinarily resonant. The pollex is not opposable, but is placed on a line with the other fingers.

In the so-called "Sakis" (Pitheciidae) the tail is sometimes long (Pithecia), sometimes short (Brachyurus), but is never prehensile, while the lower incisors are inclined forwards. The little "Night-apes" (Nyctipithecus) also have non-prehensile tails, but the lower incisors are vertical, and the eyes, in accordance with the nocturnal habits of the animal, are of immense size.

Catarhina.

The third and highest section of the Quadrumana is that of the Catarhina or Old World Monkeys. In this section the nostrils are oblique, and are placed close together, and the septum narium is narrow, the nostrils looking downwards. The thumbs of all the feet are opposable, so that the animal is strictly quadrumanous. In Colobus alone the anterior thumbs (pollex) are wanting. The dental formula is the same as in man, viz.: