Skull of Ornithosuchus and Dimorphodon 201 79. The pelvis in Ornithosaur and Dinosaur 204 80. The prepubic bones in Dimorphodon and Iguanodon 206 These figures are greatly reduced in size, and when two or more bones are shown in the same figure all are brought to the same size to facilitate the comparison. DRAGONS OF THE AIR CHAPTER I FLYING REPTILES The history of life on the earth during the epochs of geological time unfolds no more wonderful discovery among types of animals which have become extinct than the family of fossils known as flying reptiles. Its coming into existence, its structure, and passing away from the living world are among the great mysteries of Nature. The animals are astonishing in their plan of construction. In aspect they are unlike birds and beasts which, in this age, hover over land and sea. They gather into themselves in the body of a single individual, structures which, at the present day, are among the most distinctive characters of certain mammals, birds, and reptiles. The name "flying reptile" expresses this anomaly. Its invention is due to the genius of the great French naturalist Cuvier, who was the first to realise that this extinct animal, entombed in slabs of stone, is one of the wonders of the world. The word "reptile" has impressed the imagination with unpleasant sound, even when the habits of the animals it indicates are unknown. It is familiarly associated with life which is reputed venomous, and is creeping and cold. Its common type, the serpent, in many parts of the world takes a yearly toll of victims from man and beast, and has become the representative of silent, active strength, dreaded craft, and danger. Science uses the word "reptile" in a more exact way, to define the assemblage of cold-blooded animals which in familiar description are separately named serpents, lizards, turtles, hatteria, and crocodiles. Turtles and the rest of them survive from great geological antiquity. They present from age to age diversity of aspect and habit, and in unexpected differences of outward proportion of the body show how the laws of life have preserved each animal type. For the vital organs which constitute each animal a reptile, and the distinctive bony structures with which they are associated, remain unaffected, or but little modified, by the animal's external change in appearance.