11. The lowest known order of the mammalia, the _Monotremata_, represented in Australia by the duck-billed platypus (Ornithorhynchus) and the _Echidna_, is unknown in America. Considered in reference to their abundance, large size of individuals, and number of species, in comparison with the other orders present, North America may be said to be the home of _herbivores_. The only continent in rivalry with it in this respect is Africa. More abundant in individuals and species than the herbivorous mammals, however, but smaller in size and frequently diminutive, are the rodents. The carnivores are fortunately limited in number of species, although the individuals of certain species are at times numerous, but not in general dangerous to man. SOME REPRESENTATIVE MAMMALS To the general reader the animals of greatest interest are no doubt the mammals, and particularly those which attract the sportsman, are of value for food, or furnish fur and skins for clothing. Of such animals the northern portion of North America and the mountains extending southward into the austral region furnish a large number. _The Musk-Ox._--In the far north, mostly beyond the arctic circle, lives the musk-ox, the hardiest of herbivores, in which, as expressed in its generic name, _Ovibos_, there is a curious mingling of the characteristics of the sheep and the ox. The teeth are similar to those of the sheep, the female has but two mammae, and beneath the long yellowish-brown hair of the outer coat there is a thick wool-like growth. Its gentle, inoffensive nature is also similar to that of the sheep. The large feet and the horns, however, are like those of the ox tribe. The horns resemble those of the Cape buffalo, being broad at the base and covering nearly the entire forehead. They slope downward at the sides, and then curve forward and outward, at the same time tapering to a sharp point, which renders them efficient weapons. These characteristics, although intermediate between those of the sheep and the ox, are more strongly inclined to the former. In reality, however, the musk-ox is more goat-like than sheep-like, as is indicated by its covering of hair, its short sturdy legs, the cannon-bone being remarkably short, and its ability as a climber. A full-grown musk-ox measures about 8 feet in length, inclusive of the short tail, and is 3 feet, 8 or 9 inches in height at the shoulders. The thick-set, shaggy body is supported on short stout legs, and the feet are broad, to serve both as scrapers in clearing away the snow from the moss and herbage on which it lives and in climbing ice-covered slopes.