The Bradypes family is peculiar to South America. It includes but two genera, whose types are the _Chalypus-Unau_ and the _Bradypus-Ai_. The Unau, or Two-toed Sloth, is found in the forests of Peru, Guiana, and Columbia. His length is from twenty to thirty inches. He has a large head; long and dry hair, of a grayish-brown. During the day he sees very imperfectly, and therefore passes most of his time asleep upon a tree, where he may be seen clinging by three of his feet to a bough, and making use of the fourth to reach and convey to his mouth the food on which he lives. The Aï is more indolent in his habits than the Unau, from which he differs rather in his anatomical and osteological characteristics than in his aspect and conformation. He may, however, be recognized by his rudimentary tail, his flattened visage, and the long frizzled hair which covers certain parts of the body. [Illustration: 1. Aï (Two-toed Sloth). 2. Unau (Three-toed Sloth).] We have seen that the aye-aye may be considered as connecting the Quadrumana with the Bradypes, on the one hand, and the squirrels on the other. These two groups, however, exhibit a very striking contrast between their habits and disposition; and since to animals of the former the name has been given of "Sloths," the latter might justly be designated "the Active." If there exist, indeed, any animals for whom _movement_ is a vital necessity, these, assuredly, are the squirrels. They climb trees with great agility, and leap from one branch to another with a marvellous vigour and precision. On the ground, they trot rather than run. They are essentially graminivorous and frugivorous; nuts, fruits, seeds, the young stems of trees, forming their chief nourishment, though at times they plunder birds' nests, and regale themselves with the eggs or even the "callow brood." [Illustration: COMMON EUROPEAN SQUIRRELS.]