Carefully chosen was Aristotle’s name for reptiles, ‘the terrestrial, oviparous, sanguineous animals;’ for those which we are considering, breathe by lungs, and are therefore red-blooded. Cuvier divided the egg-producing animals into oviparous quadrupeds (lizards, turtles, crocodiles, and frogs); bipeds, the birds; insects and serpents. Linnæus—who, by the way, preceded Cuvier—called all reptiles ‘amphibious animals,’ of which serpents were the second order, those ‘without limbs.’ He also divided them into orders, genera, and species; but in the Ophidia was guided too much by the scales, which has caused confusion ever since, as both poisonous and harmless snakes often present similar characters in this respect. [Illustration] If the reader will turn to the illustration of scales (p. 193), he will see an example of the large scutæ or ventral plates that are possessed by the majority of the true Ophidia. The burrowing snakes, most of them small and allied to lizards in their structure, are protected by a cuirass of hard, close-set, polished scales, _alike all round_; or else with a thick, smooth skin arranged in rings. Some very poisonous serpents, notably the sea-snakes, have also the scales alike all round, because they do not require the hold which those large ventral scales afford to land serpents in progression; but it will at once be seen that on so slight a resemblance it would be unsuitable to arrange such widely-differing families in the same group. The majority of snakes have the scales under the tail different from those under the body; and a very large number, both of venomous and innocuous snakes, have broad ventral scales, as far as the termination of the body, and then a double row where the tail commences. The accompanying illustration is sufficient to convey a general idea of the arrangement of the scales before and after the anus.