Looking backwards over the many millions of years comprised in the Palaeozoic era, what may we emphasise as the most salient features? There was in the _Cambrian_ the establishment of the chief classes of backboneless animals; in the _Ordovician_ the first fishes and perhaps the first terrestrial plants; in the _Silurian_ the emergence of air-breathing Invertebrates and mud-fishes; in the _Devonian_ the appearance of the first Amphibians, from which all higher land animals are descended, and the establishment of a land flora; in the _Carboniferous_ the great Club-moss forests and an exuberance of air-breathing insects and their allies; in the _Permian_ the first reptiles and a new flora. THE GEOLOGICAL MIDDLE AGES Sec. 1 The Mesozoic Era In a broad way the Mesozoic era corresponds with the Golden Age of reptiles, and with the climax of the Conifer and Cycad flora, which was established in the Permian. But among the Conifers and Cycads our modern flowering plants were beginning to show face tentatively, just like birds and mammals among the great reptiles. In the _Triassic_ period the exuberance of reptilian life which marked the Permian was continued. Besides Turtles which still persist, there were Ichthyosaurs, Plesiosaurs, Dinosaurs, and Pterosaurs, none of which lasted beyond the Mesozoic era. Of great importance was the rise of the Dinosaurs in the Triassic, for it is highly probable that within the limits of this vigorous and plastic stock--some of them bipeds--we must look for the ancestors of both birds and mammals. Both land and water were dominated by reptiles, some of which attained to gigantic size. Had there been any zoologist in those days, he would have been very sagacious indeed if he had suspected that reptiles did not represent the climax of creation. The Flying Dragons