A deep-toned booming note came then from the hills, commencing like the warning siren of a space liner approaching its berth and swelling to a bombilation of ear-shattering sound that set the steel of the _Nomad's_ hull vibrating and their very flesh and bones a-tingle. Then it died away as had the bird note which was the first sound of this world to greet them. "Jupiter! What's that?" Mado unslung his torpedo-projector. As if in answer to his startled question, a weird object drifted over the treetops and poised directly above them, about fifty feet up. An egg-shaped thing, six or seven feet in length, and seemingly made of white metal. It swayed there gently, without visible means of support, and they could make out a transparent disk on its side, back of which there was a human head with eyes that regarded them curiously. Mado raised his torpedo tube and took aim. "Hold it!" Carr warned him. "This fellow's no savage. Probably he's one of those who tried to break our fall. Friendly, perhaps." Two more of the ovoids drifted in from the woods and joined the first one, all three settling a few feet lower and their occupants staring intently at the intruders. "I'll get the psycho-ray apparatus," Detis said excitedly. "We may be able to get thought contact with them." He dived through the _Nomad's_ entrance-manhole as he spoke. "Nothing so frightening about these creatures," Ora murmured, her eyes reproaching Carr. "Why, they seem anxious to know that _we_ are not enemies." And, indeed, this seemed to be the case, for the strange ovoids wafted still lower, dropping until a faint humming of the internal gravity mechanism came to their ears. These were a highly developed people of scientific attainment; civilized beings. But Mado kept firm hold of his torpedo tube, and Carr fingered the ray pistol at his belt. The booming note from the hills came then, frightfully near this time, and the three ovoids moved with sudden roaring of their motors, literally hurling themselves skyward. But the menace they sought to escape was real, and not to be outdone in speed. A vast black something whirred out from beyond the treetops and flung itself upon them. "A pterodactyl!" Mado gasped. "One of the prehistoric monsters of Terra!" "Carr, there are men riding it!" Ora exclaimed. "Red men!" * * * * * It was true; the pteranodon, a horrid bat-like thing with a wing-spread of fully twenty feet, carried three of the bronzed savages clinging to a sort of harness that encircled its body just back of the crested head. The huge flying reptile whistled raucously as it flew and one of the savages was whirling a sling which held a stone as large as his own head. They watched in amazement as the swift aerial steed flapped its way after the rising ovoids. And then the savage let loose an end of his thong and released its missile, which crashed full against the transparent disk of an ovoid and tore its way through.