The members of this genus, which are often kept in captivity as pets, are very small animals, covered with thick and silky fur, and having bushy tails, equal to or even exceeding the length of their body. The head is round, the eyes large and watchful, the face short and nude, and often abundantly whiskered. The mouth is large; the ears also large and often fringed, and the neck sometimes clothed, with long hair. They are distinguished from the Tamarins (_Midas_) by having their upper incisor teeth long, narrow, and protruding outwards and forwards; the incisors of the lower jaw are also very long, and its canines small and shorter than the incisors, both being protrusive, as among the Lemurs. The cranial region of the smooth skull is conspicuously large in comparison with its facial portion, but the cerebrum shows a low type of organisation, and indicates a small degree of intelligence in its possessor; it is smooth and almost devoid of convolutions; the cerebrum, too, unlike that of the _Lemuroidea_, completely covers the cerebellum. The orbits are large, and almost completely walled in from the temporal depression behind. The stomach in form resembles that found in the higher groups, but its orifices for the entrance and exit of food are nearer to each other than in any of the other American Monkeys. The female produces two or three young at a birth, instead of one, as is the general rule among the _Anthropoidea_. The species vary much in coloration, and some of them resemble the Lemurs in being ring-tailed. {132}The Marmosets are all gentle and playful in disposition, and are, on this account, very largely brought to Europe as pets; but they are very delicate, and rarely survive long in confinement after the advent of the Northern winter. They are arboreal, living in troops, and feeding on insects and fruit, and not disdaining flesh, especially of fishes, when they can obtain it. They emit a characteristic chirping noise. I. THE COMMON MARMOSET. HAPALE JACCHUS. _Simia jacchus_, Linn., Syst. Nat., i., p. 40 (1766). _Jacchus pencillatus_, Geoffr. Ann. Mus., xix., p. 119 (1812); Spix, t. c. p. 34, pl. 26 (1823). _Jacchus leucocephalus_, Geoffr., t. c. p. 119. _Jacchus vulgaris_, Geoffr., t. c. p. 119; Gray, Cat. Monkeys Brit. Mus., p. 63 (1870, in part). _Hapale jacchus_, Kuhl, Beitr., Zool., p. 46 (1820); Schleg., Mus. Pays Bas, vii., p. 271 (1876). _Hapale albicollis_, Spix, Sim. et Vespert. Bras., p. 33, pl. 25 (1823); Geoffr., Cat. Méth. Primates, p. 59 (1851). CHARACTERS.--Head small; eyes gentle; nose flat; face black, with a white spot in front; ears naked, with a tuft of long hairs on the front edge of its opening, either black, white, or grey; hair of the sides of the head elongated; back cross-banded with black and grey, the hair at the base dusky, reddish-brown in the middle, grey at the top. Tail banded with black or grey.