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 though truncate at the free extremity and hollow; they represent in a more rudimentary way the much stronger tuft at the end of the tail of other Porcupines. It is a curious fact that this and other Porcupines possess a mechanism for warning their foes precisely comparable to that of the rattlesnake. There are sixteen dorsal vertebrae.

The chief feature of this group is the existence of two pairs of incisor teeth in the upper jaw, of which the inner are very small and lie behind the outer. In the skull the infra-orbital foramen is small; the incisive foramina are very large. The tail is short or absent.

'''Fam. 1. Leporidae.'''—This family is distinguished from the Lagomyidae by the long ears, by the tail, which is present, though short, and by the longer limbs. There are six teeth belonging to the molar series in the upper jaw, and five of the same in the lower. The clavicle is imperfect.

The longest known genus of this family, Lepus, was, until the quite recent discovery of Romerolagus, the only genus. It is of universal range, excepting Australasia and Madagascar, and consists of about sixty species. These are the Hares and Rabbits, to the former being assigned the longer-limbed forms.

As every text-book of zoology contains a more or less elaborate account of the structure of the Common Rabbit, and as there is but little structural difference between the members of the genus, a short account of the generic peculiarities of Lepus will suffice here. The fore-feet are five-toed, the hind-limbs four-toed. The hairy integument enters the mouth cavity, and the inside of the cheeks have a hairy covering. The soles of the feet are, moreover, hairy. The maxillary bones are curiously sculptured.

The Common Rabbit, L. cuniculus, differs from the Common Hare in the comparatively shorter ears and legs. The ears have not, to so marked a degree, the black tips of those of the Hare. The animal, moreover, produces naked young, and lives in burrows of its own excavation. A difference in the structure of the caecum, which distinguishes the Rabbit from the Hare, has been