General Description of the Second Division of Cebidæ--Without Prehensile Tails--THE SQUIRREL MONKEYS--Described by Buffon and Humboldt--Peculiarities of the Species--Anecdotes by Le Vaillant--A Tragic End--THE WIDOW MONKEY--Origin of the Name--THE ONAPPO--Its Nocturnal Habits and Peculiar Cry--THE DOUROUCOULIS, OR OWL MONKEYS--General Description of the Family--Peculiar Formation of the Arm-bone--THE THREE-STRIPED OWL MONKEY--Described by Humboldt and Bates--THE RED-FOOTED DOUROUCOULI--THE SAKIS--Remarkable Resemblance in the Face to Man--Structural Peculiarities--THE COUXIO--THE PARAUACÚ--THE MONK--Description of the Brain--Other Varieties of the Sakis--Anecdotes of them--THE BLACK-HEADED SAKIS--General Description. None of the remaining groups or genera of these Monkeys of the New World have tails by which they can hang on with, or by the aid of which they can swing or cling when falling. Some kinds may curl the tail around a bough, or use it in their rapid side movements, after the manner of other animals, but it is never truly prehensile. This deficiency in the prehensile capacity of the tail is, of course, accompanied by an absence of the elaborate tail structures, and the end bones especially are no longer flattened, so as to grasp easily, but are round. There are other signs of their having a less elaborate conformation than the prehensile-tailed; thus, the front teeth project, or are prominent obliquely in all but one genus, and the feet and hands resemble those of quadrupeds more than ever. In fact, having descended the scale of Monkeys nearly to the bottom, resemblances with the next groups of animals are becoming more and more apparent. Just as the Monkeys of the Old World--the Baboons--resemble the carnivorous animals in many points, so these non-prehensile-tailed Monkeys of the New World have many likenesses with the Lemuroida, and with insect-eating animals, and the smaller they are the greater is the resemblance. There are two divisions of the Monkeys without prehensile tails. In one, the species have the same number of teeth as Mycetes and Ateles; and in the other they have only thirty-two teeth. In the first division are the Squirrel Monkeys, the Sakis, and the Douroucoulis, forming respectively the genera Callithrix, Pithecia, and Nyctipithecus; and in the second there are the Marmosets and Tamarins, of the genera Hapale and Midas. The second division is distinctly separated from the other by some comparative anatomists, and forms the group of “Arctopitheci,” or Bear Monkeys. GENUS CALLITHRIX[92]--THE SAIMARIS.