Part 35

Midas ursulus, var. Gray, Cat. Monkeys Brit. Mus., p. 68 (1870).

Hapale midas, Schl., Mus. Pays Bas, vii., p. 266 (1876).

CHARACTERS.--General colour black; hands and feet golden-yellow or bright rusty-red; ears short, haired. The young males resemble the adults.

DISTRIBUTION.--Surinam.

XIV. THE NEGRO TAMARIN. MIDAS URSULUS.

Midas ursulus, Geoffr., Ann. Mus., xix., p. 121 (1812); Gray, Cat. Monkeys Brit. Mus., p. 68 (1870).

Midas tamarin, Slack, Proc. Acad. Nat. Sc. Philad., 1861, p. 464.

Hapale ursula, Schl., Mus. Pays Bas, vii., p. 265 (1876).

CHARACTERS.--Body long, slender, covered with soft thick fur; ears large, naked; the face haired. General colour black; nose and lips black; hinder part of the body rather mottled or banded with reddish-brown or greyish-white; the hands sometimes black and sometimes yellow. Length, 9 inches; tail, 15 inches.

DISTRIBUTION.--Found on the Lower Amazon, near Para. Mr. Bates says it is not met with in the Upper Amazon Region, but in its stead a closely allied species (Midas nigricollis), presents itself.

{149}HABITS.--"The Midas ursulus is never seen," writes Mr. Bates, "in large flocks; three or four is the greatest number observed together. It seems to be less afraid of the neighbourhood of Man than any other Monkey. I sometimes saw it in the woods which border the suburban streets, and once I espied two individuals in a thicket behind the English Consul's house at Nazareth. Its mode of progression along the main boughs of the lofty trees is like that of the Squirrels; it does not ascend to the slender branches, or take wonderful flying leaps like those Monkeys whose prehensile tails and flexible hands fit them for such headlong travelling. It confines itself to the larger boughs and trunks of trees, its long nails being of great assistance to the creature, enabling it to cling securely to the bark; and it is often seen passing rapidly round the perpendicular cylindrical trunks. It is a quick, restless, timid little creature, and has a great share of curiosity, for when a person passes by under the trees along which a flock is running, they always stop for a few moments to have a stare at the intruder." In Para, the Negro Tamarin "is often seen in a tame state in the houses of the inhabitants.... When first taken, or when kept tied up, it is very timid and irritable. It will not allow itself to be approached, but keeps retreating backwards when anyone attempts to coax it. It is always in a querulous humour, uttering a twittering, complaining noise; its dark, watchful eyes, expressive of distrust, are observant of every movement which takes place near it. When treated kindly, however, as it generally is in the houses of the natives, it becomes very tame and familiar.... It is generally fed on sweet fruits, such as the banana; but it is also fond of insects, especially soft-bodied spiders and grasshoppers, which it will snap up with eagerness when within {150}reach. The expression of countenance in these small Monkeys is intelligent and pleasing. This is partly owing to the open facial angle, which is given as one of 60°, but the quick movements of the head, and the way they have of inclining it on one side, when their curiosity is excited, contribute very much to give them a knowing expression.... In mobility of expression of countenance, intelligence and general manners, these small Monkeys resemble the higher Apes far more than they do any rodent animal with which I am acquainted, notwithstanding their apparently low organisation in many points."

This description of the habits of the Negro Tamarin may be taken as representative of those of the various species of the genus, of whom only glimpses can be caught in their homes, which are the safe altitudes of the giants of the virgin forests of Brazil.

THE CAPUCHINS, HOWLERS, AND SPIDER-MONKEYS, &c. FAMILY CEBIDÆ.

This family embraces the typical Platyrrhine Monkeys, and to it belongs the great majority of the American species. As already pointed out (p. 127) their nose is flat, and the partition between the nostrils, which open sideways, is very broad, and separates them widely. They are essentially quadrupedal, and walk with the soles of both pairs of limbs flat to the ground. The Spider-Monkeys occasionally, however, assume an erect posture. "They all possess tails, and in some genera (e.g., Ateles) this organ becomes very flexible and muscular, and the under surface of its curled extremity is devoid of hair and highly sensitive. The tail thus modified is a powerful prehensile organ and serves for a fifth hand." (Huxley.) In these {151}Monkeys there are no cheek-pouches, nor ischial callosities. Except in the Spider-Monkeys the hind-limbs are longer than the fore-; "while the thumb, even where it is best developed, is capable of but a partial opposition to the other fingers, bending almost in the same plane with the latter, so as to be more like a fifth finger." (Mivart.) Nevertheless, all its muscles, except the long flexor, are present. The great-toe is large and can be moved from and to the side of the other digits, but is not opposable to them.

The skull is smooth and has no muscular crests; the external bony tube to the ear is not ossified. The two extremes in its form are presented by the Howling Monkeys (Alouatta) and the Squirrel-Monkeys (Chrysothrix), as pointed out by Professor Huxley in his "Anatomy of Vertebrated Animals": "In the former the face is very large and prominent, with a low facial angle. The roof of the brain-case is depressed; the plane of the occipital foramen [for the passage of the spinal cord] is almost perpendicular" to the axis of the base of the skull. "In Chrysothrix, on the contrary, the face is relatively small, with a high facial angle; the brain-case is moderately arched;" and the plane of the occipital foramen is horizontal.

The dentition of the Cebidæ is very characteristic of the family. The dental formula is I2/2, C1/1, P3/3, M3/3 and the teeth thirty-six in all--a larger number than is found in any of the Old World forms, or in the species of the last family (the Hapalidæ); for they possess an extra pre-molar tooth above and below on each side. Their molar teeth are four-cusped; and in the upper molars of the Spider-Monkeys (Ateles) and of the Howlers (Alouatta) there is an oblique cusp, such as is found in the molars of the Lemuroidea, joining the hind inner to the front outer cusp. Among the Cebidæ the brain varies {152}very much; the posterior lobes of the main brain (or cerebral hemispheres, which are almost always convoluted) are also almost always so large as to entirely cover over the cerebellum (or hind brain), a relation which does not exist between these two regions of the brain in the Lemuroidea. The cerebellum, however, in the Howlers is slightly uncovered. The absolute size of the brain never, in any Ape, approaches that of Man. None of the Cebidæ attain the size of even the medium-sized Old World Apes.

The Cebidæ are all arboreal, and strictly confined to the forest regions of Tropical America, from the southern part of Mexico to about the parallel of 30° S. lat. They are divided into four sub-families, namely: The Douroucolis, or Night-Monkeys (Nyctipithecinæ); the Saki Monkeys (Pitheciinæ); the Howlers (Mycetinæ); and the Capuchin Monkeys (Cebinæ).

THE NIGHT-MONKEYS. SUB-FAMILY NYCTIPITHECINÆ.

The Night-Monkeys are small and elegant animals covered with long hair, and having long bushy tails, which are not prehensile, although they can be curled round a branch of a tree. The caudal vertebræ in these creatures are consequently not flattened from above downward, as is the case in the prehensile-tailed groups, but rounded. Their lower incisor teeth are set vertically and their thumb is fairly well developed.

This sub-family contains three genera, the Squirrel-Monkeys (Chrysothrix); the Whaiapu-Sais, or Titis (Callithrix); and the typical Night-Monkeys, or Douroucolis (Nyctipithecus).

THE SQUIRREL-MONKEYS. GENUS CHRYSOTHRIX.

Chrysothrix, Kaup., Thierreich., i., p. 51 (1835).

{153}The Saimiris, or Squirrel-Monkeys, are very beautiful and active little animals, characterised by their soft, close, and erect fur, and especially in having the head produced posteriorly. The face is relatively small and has a high facial angle. The eyes are large, directed forwards, and set very close together. The ears are large; and the nose has a very broad partition between its nostrils. The tail is long, round, and covered with short hair; but tufted at the extremity and non-prehensile.

As regards the skeleton, the skull is elongated, and the arched cranial portion prolonged backwards, the length of the base of the skull being shorter than the cerebral cavity. The facial portion of the skull is relatively smaller and the cranial larger even than in Man; this character being, however, common to all the smaller representatives of particular groups, and "obviously necessary to provide the requisite amount of brain-space." (Mivart.) The angle of the lower jaw is narrow behind. The bony partition between the nostrils is very thin and membranaceous; and that between the large orbits is also thin and imperfect. The lower incisor teeth are vertical, and in regular series with the canines, and the latter are well developed. No Primate has the teeth placed in one uninterrupted series except Man; but there is always a small interval between each upper canine and the adjacent incisor, and between each lower canine and the adjacent pre-molar.

The skeleton of the hand is one-fifth of the length of the spinal column. The wrist-bones are nine in number, the central--os centrale--being present as in the majority of Monkeys. In Chrysothrix and in Nyctipithecus also, the thumb is proportionately shorter than in any other genus, except among the Spider-Monkeys (Ateles), and the Old World {154}Guerezas (Colobus). In the length of their foot the members of this genus approximate to the proportion existing in Man; and its length, compared with that of the hand, is greater in Chrysothrix than in any other group of Monkeys.

The cerebral hemispheres project beyond the hind brain (cerebellum) to a greater relative extent than in any other mammal, namely, to one-fifth of their total length. (Huxley.) The external surface of the cerebral hemispheres is almost as little convoluted as in the Marmosets and Tamarins, in which it is almost quite smooth, yet on the inner faces of the hemispheres the more important grooves (sulci) are present. The opening for the passage of the spinal cord lies nearly in the middle of the base of the skull, whereas in other genera it is situated closer to the hinder region.

The Squirrel-Monkeys are entirely arboreal, and found in most of the tropical regions from Costa Rica to Brazil and Bolivia, being among the commonest of the Anthropoids of the American forests. They are diurnal, and feed chiefly on insects; but they will also often attack and devour small birds.

I. THE SHORT-TAILED SQUIRREL-MONKEY. CHRYSOTHRIX USTA.