One of the gnus has a brindled neck and forequarters, pale streaks on a dark ground, and a black and tufted tail; another has a white tail covered with long hair from its base, and shows no brindling. The latter has an almost straight back, whilst the former stands higher in its forequarters like the bison. The horns of the brindled black-tailed gnu do not pass forwards nearly so much as those of the other. All the Gnus are South African and would appear to bear the same relation to the buffaloes of that continent that the North American bison does to the American buffalo. They are active but rather awkward animals, and their self-important airs are sometimes amusing. THE SKULL OF THE DUGONG, OR HALICORE. This animal is allied to the Manati, both belonging to the order _Sirenia_. They are water-living mammals. The dugong occurs only in Eastern and Australian seas, the manati on the coasts of South America and Africa. The grotesquely misshapen aspect of the skull of the dugong is due to the enormous development of the bones in its upper jaw which carry the cutting teeth (premaxillary bones and incisor teeth), and its clumsy lower jaw. The former bear a tusk in the male, which in the female is present but is never cut. There are no canine teeth, and in the massive lower jaw no incisor teeth are ever cut. The rudiment of one is, however, present in the jaw. It may be noted that the bones carrying the upper incisors do not become united to those of the upper jaw. The back teeth (chewing teeth), are only four, five, or six in number in the dugong, whereas in the manati there may be twenty. A remarkable tendency to vary in their dentition is characteristic of this group of animals, and is no doubt in relation with differences in food. A recently extinct member of the family (Steller’s sea-cow) had no teeth at all, but masticated the soft sea-weeds on which it fed by the aid of a horny palate (_Rhytina Stelleri_). HEAD OF THE WART HOG (_Phacochœrus Æthiopicus_). The Wart Hog is a native of Africa. His name makes reference to a pair of wart-like excrescences, which are formed, one under each eye. These may be an inch and a half in length. There is an enormous development of the base of the zygoma. The incisor teeth in the upper jaw are often wanting, and sometimes those in the lower also. The snout is short and square. The so-called warts are fleshy skin-growths and may be large enough to look like ears. There is another Wart Hog (_Œliani_), met with in Abyssinia. It differs from the Cape Wart Hog in that its incisor teeth in both jaws are more persistent. It has two “warts.” THE SKULL OF A PIG (_Sus scrofa_).