“Double your thumb under, put the three fingers close together but not quite touching, and spread the little finger out,” ordered his friend. Perry obeyed. “Now, imagine you have claws on the three fingers, and make your little finger four feet long. Next picture to yourself a skin like a bat’s stretched from the tip of the finger to your feet and you have a Pteranodon.” “Just like a big bat!” “No, no. The bat has five fingers. The bat’s thumb is a claw, and the membrane that makes the wing is like a big web between the long, long fingers. Quite different. Then the bat is a mammal. The Pteranodon, like all the flying lizards, was a reptile. The first bat was not born until thousands of years after the last pterodactyl or flying lizard died. There were lots of different kinds, but all their flying planes, or wings, were stretched from one finger. That’s the reason of the name, Perry, ptero—dactyl, wing—finger. Some were smaller than a sparrow, others were big. The Pteranodon was the biggest. Some had teeth, some had beaks like birds. There was the Ramphorhyncus—” “Oh, I know him,” said the boy eagerly, “he had a tremendous long tail with a rudder at the tip.” “Yes, yes,” agreed his friend. “And do you know the Dimorphodon Macronyx?” “Big-headed thing, looks like a nightmare, with a rat’s tail, teeth sticking up on the outside, and eyes that look as if he’d been in a fight? Is that the one?” Antoine laughed at the description. “It is not quite scientific, worded that way,” he answered, “but you have the idea. That is ‘him,’ as you say. None of these really flew. They aëroplaned.” “I don’t quite understand,” said the boy. “How do you mean they aëroplaned?” “See,” said his friend, “a bird flaps his wings and rises. Some birds can glide for hours and hardly ever flap their wings. But many of the flying lizards could not flap their wings at all. They had to climb up a tree or a cliff with their claws and then throw themselves into space. Then, with the start they thus got, they could swoop and glide and swirl for quite a long time. When the spurt was over, they would have to find some new place up which to climb. Some of them, if they were on a flat plain, would die.” [Illustration: _Courtesy of American Museum of Natural History._ THE LARGEST CREATURE THAT EVER FLEW. Pteranodon, the flying reptile, twenty-one feet from tip to tip of “wings,” the last of a giant race, soaring over the Cretaceous ocean.] [Illustration: _Courtesy of D. Appleton & Co._ A FLYING NIGHTMARE OF OLDEN TIME. Dimorphodon Macronyx, size of a small dog, one of the minor terrors of the air, ten million years ago. Restoration from Seeley, in “Dragons of the Air”; pose of restoration questionable, as fore-legs could not be used for walking.] “Even the Pteranodon?”