The Saimiri is commonly known by the name of the _Aurora_, the _Orange_, or _Yellow Sapajou_. It is very common at Guiana, for which reason many travellers have styled it the _Cayenne Sapajou_. From the gracefulness of its motions, the smallness of its size, the brilliant colour of its coat, the fullness and brightness of its eyes, and its small round visage, the saimiri has ever taken the lead of every other sapajou, and it is, in fact, the most beautiful and pleasing of this tribe; but it is also the most delicate and the most difficult to transport and preserve. From these characters, and particularly from that of the tail, which may be said to be but half prehensile, for though it makes use of it to climb up trees, yet it can neither strongly hold, nor firmly fix itself by it, it seems to form the shade between the sapajous and the sagoins. _Distinctive Characters of this Species._ The saimiri has neither pouches on each side the cheeks, nor callosities on the posteriors. The partition which divides the nostrils is thick, and the apertures are placed on the side and not under the nose. He may be said to have no forehead. His hair is of a bright yellow colour; and he has two flesh-coloured rings round the eyes. His nose is elevated at the root, and flat towards the nostrils. The mouth is small, the face flat and naked, and the ears are garnished with hair and a little pointed. The tail is half-prehensile and longer than the body. He is scarcely more than ten or eleven inches in length. He stands on his hind feet with great ease, but he commonly walks on all fours. THE SAKI. The Saki, (_fig. 216._) commonly called the _Fox-tailed Monkey_, from its tail being cloathed with very long hair, is the largest of the sagoins, being above seventeen inches long when full grown, whereas the largest of the other five species is not above nine or ten. The saki has very long hair on its body, and still longer on its tail: its face is red, and covered with a whitish down: it is easy to be known and distinguished from every other sagoin, sapajou, or monkey, by the following characters: _Distinctive Characters of this Species._