The Tilgate beds of the Wealden series, just mentioned, have yielded numerous fragments of the most remarkable reptilian fossils yet discovered, and whose wonderful forms denote them to have thronged the shallow seas and bays and lagoons of the period. In the grounds of the Crystal Palace at Sydenham the reader will find restorations of these animals sufficiently perfect to illustrate this reptilian epoch. They include the _iguanodon_, an herbivorous lizard exceeding in size the largest elephant, and accompanied by the equally gigantic and carnivorous _megalosaurus_ (great saurian), and by the two yet more curious reptiles, the _pylæosaurus_ (forest, or weald, saurian) and the pterodactyl (from _pteron_, ‘wing,’ and _dactylus_, ‘a finger’), an enormous bat-like creature, now running upon the ground like a bird; its elevated body and long neck not covered with feathers, but with skin, naked, or resplendent with glittering scales; its head like that of a lizard or crocodile, and of a size almost preposterous compared with that of the body, with its long fore extremities stretched out, and connected by a membrane with the body and hind legs. Suddenly this mailed creature rose in the air, and realised or even surpassed in strangeness _the flying dragon of fable_: its fore-arms and its elongated wing-finger furnished with claws; hand and fingers extended, and the interspace filled up by a tough membrane; and its head and neck stretched out like that of the heron in its flight. When stationary, its wings were probably folded back like those of a bird; though perhaps, by the claws attached to its fingers, it might suspend itself from the branches of trees. MAMMALIA IN SECONDARY ROCKS.