Humboldt’s new Monkey had a prehensile tail which was longer than the body, and underneath, close to the tip, there was a naked and sensitive spot of some length. It had a round and large head, a naked black face, but no beard. There were, however, smellers or long hairs around the mouth. It had long limbs and a shortish body, whose fur was long and sable-grey in colour. A good temper and a quiet disposition appeared to characterise this Monkey, and the natives said it was found in troops, and that it often stood upon its hind legs. They have thumbs, as well shaped as those of any American Monkey, on the fore hands, as well as on the hinder extremities. They were deficient, however, in the howling apparatus, and therefore they differ from the Mycetes, and as their thumbs were noticed to be large, they differ from the next group of Monkeys, or the Spider Monkeys. A careful examination of the skeleton shows that the outside differences are accompanied by inside ones, especially in the skeleton. Thus, there are fourteen rib-bearing back-bones, or vertebræ, and this increase of number over the ordinary thirteen is interesting, because it makes the animal approach those lower than the Primates; then it has four loin vertebræ, and three are in the sacrum bone. There is a curious growth of the second vertebra of the neck or the axis, for its spine is trifid, and has three projections for the attachment of muscles. Finally, the long tail is very elaborate in its bony part, and seven of its bones near the root have so great a resemblance to the back-bones higher up in the body, that they have a canal like that which in the others protects the spinal marrow, which, however, does not reach further down than the lower loins. Then five of them have good strong spines, and all have the chevron or V-shaped bones underneath well grown. This tail is quite as useful to the Lagothrix as it is to the Howlers and to the Spider Monkeys about to be considered, and they feel with, and swing and hold by it, to perfection. The Caparro is about two feet two inches in length without the tail, and has been subsequently to its description by Humboldt called _Lagothrix Humboldtii_, or Humboldt’s Lagothrix. THE BARRIGUDO.[81]