So I have again written out my lectures, with the aid of the latest discoveries, and the story of animal structure has lost nothing in interest as a twice-told tale. It still presents in epitome the story of life on the Earth. He who understands whence the Flying Reptiles came, how they endured, and disappeared from the Earth, has solved some of the greatest mysteries of life. I have only contributed something towards solving the problems. In telling my story, chiefly of facts in Nature, an attempt is made to show how a naturalist does his work, in the hope that perhaps a few readers will find happiness in following the workings of the laws of life. Such an illumination has proved to many worth seeking, a solid return for labour, which is not to be marketed on the Exchange, but may be taken freely without exhausting the treasury of Nature's truths. Such outlines of knowledge as here are offered to a larger public, may also, I believe, be acceptable to students of science and scientific men. The drawings given in illustration of the text have been made for me by Miss E. B. Seeley. H. G. S. KENSINGTON, _May, 1901_ CONTENTS PAGE CHAPTER I. FLYING REPTILES 1 CHAPTER II. HOW A REPTILE IS KNOWN 4 CHAPTER III. A REPTILE IS KNOWN BY ITS BONES 11 CHAPTER IV. ANIMALS WHICH FLY 15 CHAPTER V. DISCOVERY OF THE PTERODACTYLE 27 CHAPTER VI. HOW ANIMALS ARE INTERPRETED BY THEIR BONES 37 CHAPTER VII. INTERPRETATION OF PTERODACTYLES BY THEIR SOFT PARTS 45 CHAPTER VIII. THE PLAN OF THE SKELETON 58 CHAPTER IX. THE BACKBONE, OR VERTEBRAL COLUMN 78 CHAPTER X. THE HIP-GIRDLE AND HIND LIMB 93 CHAPTER XI. SHOULDER-GIRDLE AND FORE LIMB 107 CHAPTER XII. EVIDENCES OF THE ANIMAL'S HABITS FROM ITS REMAINS 134 CHAPTER XIII. ANCIENT ORNITHOSAURS FROM THE LIAS 143 CHAPTER XIV. ORNITHOSAURS FROM THE MIDDLE SECONDARY ROCKS 153 CHAPTER XV. ORNITHOSAURS FROM THE UPPER SECONDARY ROCKS 172 CHAPTER XVI. CLASSIFICATION OF THE ORNITHOSAURIA 187 CHAPTER XVII. FAMILY RELATIONS OF PTERODACTYLES TO ANIMALS WHICH LIVED WITH THEM 196 CHAPTER XVIII. HOW PTERODACTYLES MAY HAVE ORIGINATED 213 APPENDIX 231