Though all animals be fitted by nature for the life which their instincts teach them to pursue, naturalists have learned to recognise among them certain aberrant and mutilated forms, in which the type of the special class to which they belong seems distorted and degraded. They exist as the monster families of creation, just as among families there appear from time to time monster individuals,—men, for instance, without feet, or hands, or eyes, or with their feet, hands, or eyes grievously misplaced,—sheep with their fore legs growing out of their necks, or ducklings with their wings attached to their haunches. Among these degraded races, that of the footless serpent, which “goeth upon its belly,” has been long noted by the theologian as a race typical, in its condition and nature, of an order of hopelessly degraded beings, borne down to the dust by a clinging curse; and, curiously enough, when the first comparative anatomists in the world give their readiest and most prominent instance of degradation among the denizens of the natural world, it is this very order of footless reptiles that they select. So far as the geologist yet knows, the Ophidians did not appear during the Secondary ages, when the monarchs of creation belonged to the reptilian division, but were ushered upon the scene in the times of the Tertiary deposits, when the mammalian dynasty had supplanted that of the Iguanodon and Megalosaurus.