With the Cavies concludes the long series of simple-toothed Rodents, and some of them, as we have seen, present no small resemblance to the Hares and Rabbits which constitute the greater part of the second great group into which we have divided the order. The chief peculiarity of this section, as has been already stated, consists in the presence in the upper jaw of a pair of minute incisor teeth, placed immediately behind the large effective incisors; and in the newly-born animal the number of these teeth is even greater, there being six incisors in the upper jaw, two of which fall out at an early period. Though the number of species included in this section is very considerable (about fifty, according to Mr. Wallace’s estimate), it includes only two families, and each of these contains only a single genus. We will commence with that which includes the best-known forms, the Hares and Rabbits. [Illustration: CAPYBARA.] FAMILY XVII.--LEPORIDÆ (HARES AND RABBITS). The general appearance of these animals hardly needs to be described, and we may, therefore, indicate merely the structural peculiarities which serve to define the family. These consist in the presence of six rootless molars on each side in the upper, and five in the lower jaw (_see_ figure on p. 82), each molar being divided into lobes by transverse folds of enamel; in the compressed form of the skull and the presence of wing-like post-orbital processes of the frontal bones; in the imperfect condition of the clavicles; the greater development of the hind limbs; and the presence of a short, bushy, upturned tail. The ears are long; the inner surface of the cheeks is more or less clothed with short hairs; the fore-limbs have five, and the hind-limbs only four toes; and the soles of the feet are hairy throughout. In all these characters, however they may differ in some respects, all the true Hares and Rabbits agree. The representatives of this family occur in nearly all parts of the world, but chiefly in the northern hemisphere, and the few species which pass down within the tropics are generally found only in mountainous regions. In the north they reach the Arctic regions in both continents. In the Old World a few species are scattered over India and Further India, and four or five occur in Africa, but chiefly in the southern part of the continent. In North America the species are numerous, and some of them range southward into Central America; but South America has only a single species, which occurs in the mountains of Brazil and upon the Andes. As the whole of the family consists of animals to which in common parlance the names of Hares and Rabbits are given, we may take as examples of it the Hares and Rabbits which are so abundant in Great Britain, the other species agreeing generally with one or other of them in character and habits.