The sun touched the rim of the horizon. At the same instant, with a sucking sound, the vast bulk of a Diplodocus squirmed up from the slough and poised its ungainly head, as though to see. A leaping Compsognathus loomed black against the sky. Noiseless, but menacing, a winged Pteranodon, twenty-one feet from tip to tip of wing, soared heavily above him. A pigmy in a world of giant monsters, the boy raced on, speeding from—he knew not what, to—he knew not whither. The sense of terror from the monstrous brood became more keen as a closer peril grew. His knees ached almost beyond endurance from the strain of trying to keep his seat, for no horsemanship could avail upon such a steed as that which he was riding. The long jerking leaps, though they covered ground amazingly, seemed to drag him inside out at every stride. The red-brown neck stretched far ahead, and gleaming in the dull-red dusk jutted the single horn, spirally twisted like a kudu’s and lengthening even as he looked at it. Suddenly, without an instant’s warning, the beast threw back his head. The gleaming horn jerked to within a few inches of the boy. The lad paled. “Next time—” he said. What could he do next time? Without pausing, the Thing sped on, racing like the wind over a mountainless world, so that Perry did not dare throw himself off its back. Lower sank the sun, till only one-half of its orb was seen, its beams lying level over the plain that saw never a hill over its thousand miles of length. Worst of all, instead of the kinship between steed and rider that gives strength in the most desperate pursuit, he felt the malevolence of the evil thing he bestrode, and tried to brace his nerve against an attack from his sole means of escape from this browsing ground of swollen reptiles. He had not long to wait. In mid-leap, the creature checked its speed, plunging stiff-legged, at the same time tossed back its now long and twisted horn to pierce him to the vitals. Tense for the spring, Perry thrust himself upwards from the knees, the sudden stoppage throwing him over the creature’s head. Well he knew that if he fell on the ground sharp hoof and sharper horn would pin him to the earth. He grabbed the horn as it slid under him, and clung to it like death. In fury, the unicorn tossed him as a terrier does a rat. The boy felt his hold weakening, but he clung desperately. Sight and hearing failed him, yet he clutched blindly, till with a wrench the strained finger-clasp gave way and he found himself flying through the air. Fortune favored him. He landed on his feet, and though he staggered, he did not actually fall. The second’s recovery sufficed to clear his wits, and he dodged as the vicious creature lunged. Before him loomed the vast bulk of a Brontosaurus and behind this he ran, trusting for safety to the small brain and sluggish movements of the giant.