_Callithrix castaneoventris_, Gray, Ann. and Mag. N. H., xvii., p. 58 (1866); id., Cat. Monkeys Brit. Mus., p. 56 (1870). _Callithrix caligata_, Wagner, Arch. f. Naturg., 1842, i., p. 454 (ex Natterer, MSS.); Schl., Mus. Pays Bas, vii., p. 237 (1876). CHARACTERS.--Fur of the same nature as in _C. cuprea_, black, ringed with grey; face grizzled, whiskers, throat, chest, under side of the body, and inner surface of the limbs reddish-chestnut; outside of the limbs grizzled, washed with rufous; forehead, hands, feet and tail black; tip of the tail paler. DISTRIBUTION.--Paraguay and Brazil; Borba, Rio Madeira. The two following species may be distinguished from those already described by having their soft woolly fur entirely free from the long bristly hairs, which were dispersed through the fur of the others. {165}X. THE BLACK-HANDED TITI. CALLITHRIX MELANOCHIR. _Callithrix melanochir_, Neuwied, Beitr., ii., p. 114, et Abbild., iv.; Gray, Cat. Monkeys Brit. Mus., p. 57 (1870); Schl., Mus. Pays Bas, vii., p. 233 (1876). CHARACTERS.--General colour red, but the crown of the head, the throat, and inner side of the limbs, mixed black and grey; the hands and feet black. DISTRIBUTION.--This species has been recorded from Bahia, on the east coast of Brazil. XI. THE GREY TITI. CALLITHRIX GIGOT. _Callithrix gigot_, Spix, Sim. et Vespert. Bras., p. 22, pl. 16 (1823); Schl., Mus. Pays Bas, vii., p. 234 (1876); Weldon, P. Z. S., 1884, p. 6. _Callithrix gigo_, Gray, Cat. Monkeys Brit. Mus., p. 57 (1870). CHARACTERS.--Hair about two inches long, soft and slightly woolly over the trunk; hair on the forehead shorter and more thickly set; that over the limbs short and loose. General colour of the back reddish-grey behind, more ashy over the forehead and limbs; the hair black at the base, cream-coloured further up, the tips ringed with chestnut and black. Muzzle and chin black, with a few short, strong, white hairs; a black line along the nose and round the eyes; the eyelids white; the eye-lashes and long eye-brows black; forehead thickly covered with loose grey hairs, slightly tipped with black; a faint ridge across the brow between the ears; the ears black, covered with soft black hairs, except for a small grey tuft at their hind outer angle. In front of the ears a light grey band over the cheeks, continued above on to the forehead, below to the chest; throat naked, light pink; under surface {166}of the limbs pale grey; the hands and feet black; tail red, the hair bushy at its base. Length of the body, 14 inches; of the tail, 13½ inches. (_Weldon._) Cæcum with dilated end; liver more divided than in _C. moloch_; the two halves (_rami_) of the lower jaw enormously deep, resembling those of the Howlers (_Mycetes_). DISTRIBUTION.--Brazil; Bahia, and the country between the Parahyba and the mountains to the north of the Bay of Rio de Janeiro. HABITS.--This species is very rare, and nothing is known of its habits.