“From Australia to the Arctic Circle the whole world was in their grip, and one can almost picture two of the great monsters thinking, in their sluggish way, of the impossibility that their mighty lordship should ever come to an end. I say ‘almost,’ Perry, for you know that these creatures had very little brain. A monster weighing thirty tons, like the Brontosaurus, had only one-quarter as much true brain as an ape of to-day. They could hardly think at all. Yet, in some brute way, they knew that they had nothing but each other to be afraid of. The enemy that should conquer them they did not know. [Illustration: _Courtesy of American Museum of Natural History._ THE SHARP-TOOTHED DEATH. Thirty-foot Tylosaurus pursuing Portheus, the six-foot bulldog fish, in the Jurassic ocean.] [Illustration: _Courtesy of American Museum of Natural History_. THE JURASSIC SEA-SERPENT. Elasmosaurus, the scourge of the primitive ocean, seventy feet in length, ravaging the bottom of the shallow sea. Neck less flexible than shown in restoration.] “Then came the cold, the awful cold that drove the Pterodactyls from the earth. The warm seas of the Age of Chalk grew chill, the land rose, the water ran into the deep beds of what is now the Atlantic and Pacific Oceans, the continents as we know them took their shape, the ever-rising earth grew impatient of its slow-brained huge inhabitants, and shook them off. The Tyrannosaurus and all the flesh-eating dinosaurs had found easy prey on the huge vegetarian monsters, but as these decreased they began to prey upon themselves. Their heavy shapes and their slow brains, however, made them unfit for the great battle of life, and quicker and more alert animals took their place. “When, a hundred thousand years later, the climate relaxed and began to grow warmer again, in the Eocene Epoch, at the beginning of the Tertiary Period, the mighty monsters and the strange dragons were all gone, and a ragged regiment of crocodiles, turtles, and serpents in the tropics, with a swarm of smaller creatures, such as lizards, in the fringes of the warm zone, was all that remained of the world-conquering hosts of the Mesozoic reptiles. “There are none left now, Perry, and you will wear out your eyes with watching over the sea before ever you will see any of the sea-snake-lizards—the Dolichosaurs and the Mosasaurs, or the fish-lizards—such as the Ichthyosaurus. The Plesiosaurus, too, have gone. Not one of those big sea-reptile forms has sought its prey in the waters of the earth for at least three million years.” “Yet lots of people claim to have seen sea-serpents,” protested Perry. “Plenty of them. But no one has ever made a photograph of one, nor has a single specimen of one ever been put into a Museum,” remarked the professor. “Do you think they were all fake—I mean mistakes?” corrected the boy, hastily.