straddled the space, resting its hands on the palms and tips of the outstretched fingers with the knuckles bent at an acute angle, and thus mounted to the top with the greatest facility. Although seeming to prefer insects, it ate all kinds of fruit, but would not touch raw or cooked meat, and was very seldom thirsty. I was told by persons who had kept these Monkeys loose about the house, that they cleared the chambers of bats as well as insect vermin. When approached gently, my Ei-á allowed {173}itself to be caressed; but when handled roughly it always took alarm, biting severely, striking with its little hands, and making a hissing noise like a Cat. "I have mentioned the near relationship of the Night-Apes to the Sai-miris (_Chrysothrix_), which are among the commonest of the ordinary Monkeys of the American forests. This near relationship is the more necessary to be borne in mind, as some Zoologists have drawn a comparison between them and the nocturnal Apes of the Lemur family, inhabiting Ceylon and Java, and it might be inferred that our American Ei-ás were related more closely to these Old World forms than they are to the rest of the New World Monkeys. The large nocturnal eyes and short ears of the Eastern Lemurs are simply resemblances of analogy, and merely show that a few species, belonging to utterly dissimilar families, have been made similar by being adapted to similar modes of life...." THE SAKIS. SUB-FAMILY PITHECIINÆ. The Sakis are characterised by having their lower incisor teeth inclined forward at their summits somewhat as among the Lemurs; and separated from the long canines by an interspace. The molar teeth are small; the tail, which in some is long, in others short, is non-prehensile. The nostrils are, as usual, far apart, and the thumb is well developed. The ears are large. Great differences in the character of the fur exist in the group: some species having long hair over the whole body, others on the chin and cheeks; some are well bearded, while others again are quite bald. The Sakis are divided into two genera, a short-tailed group (_Brachyurus_), containing the Uakarí Monkeys, and a long-tailed {174}section, the Sakis (_Pithecia_). Their various species are restricted to the great equatorial forests of South America. THE UAKARÍ MONKEYS. GENUS BRACHYURUS. _Brachyurus_, Spix, Sim. et Vespert. Bras., p. 11 (1823); W. A. Forbes, P. Z. S., 1880, p. 644. _Ouakaria_, Gray, P. Z. S., 1849, p. 9.