river what should they come upon but whole skeletons of Iguanodons. In the days of long ago the great beasts had come down to the river to drink, and had got "bogged" in the soft clay. The skeletons were carefully got out, and set up in the Museum at Brussels. Without going so far as that, you may see in the Natural History Museum in London, or the Geological Museum at Oxford, a facsimile of one of these skeletons, large as life, and have some idea of the sort of beast the Iguanodon was. I should tell you why he was so named. Before it was known what he was like in general form, it was found that his teeth, which are of a remarkable character, were similar to those of the Iguana, a little lizard of the West Indies. So he was called Iguanodon,--an animal with teeth like the Iguana (fr. _Iguana_, and Gk. $odous$ g. $odontos$ a tooth). He was quite a harmless beast, though he was so large. He was a vegetarian. There were other great reptiles, more or less like him, which were also vegetable feeders. But there were also carnivorous reptiles, generally smaller than the herbivorous, whose teeth tell us that they preyed on other animals. [Illustration: PL. I] Perna Mulleti Meyeria Vectensis (Atherfield Lobster) Panopaea Plicata Terebratula Sella Cyrena Limestone Iguanodon Vertebra WEALDEN AND LOWER GREENSAND Those were the days of reptiles. Now the earth is the domain of the mammalia. But then great reptiles like the Iguanodon wandered over the land; great marine reptiles, such as the Plesiosaurus, swam the waters; and wonderful flying reptiles, the Pterodactyls, flew the air. Some species of these were quite small, the size of a rook: one large species found in the Isle of Wight had a spread of wing of 16 feet. Imagine this strange world,--its forests with pines and monkey puzzles and cycads,--ferns also, of which many fragments are found,--its great reptiles and little reptiles, on land, in the water and the air. Were there no birds? Yes, but they were rare. From remains found in Oolitic strata,--somewhat older than the Wealden,--we know that birds were already in existence; and they were as strange as anything else. For they had jaws with teeth like the reptiles. They had not yet adopted the beak. And instead of all the tail feathers starting from one point, as in birds of the present day, these ancient birds had long curving tails like reptiles, with a pair of feathers on each joint. Birds of similar but slightly more modern type have been found in Cretaceous strata (to which the Wealden belongs) in America, but so far not in strata of this age in Britain.