"Come along. There's the cave mouth just ahead."
The chums paused to stare at the tall posts that marked the entrance, each crowned with a polished human skull, then Raal got the torches flaring and passed them out to light their way.
Dick followed close beside Raal, with Dan at his heels, as they plunged into the darkness of the cave. The narrow walls rose straight beside them as they proceeded slowly, and soon Dick reached the place where the passage turned at right angles.
Here the walls were flat surfaces, smoothed and cut artificially. It was no longer a rugged cave but a tunnel.
"Look!" exclaimed Dan. "The walls are all covered with drawings."
Dick held up his torch to the rocky surface and saw that it was painted with pictures of hunting scenes, men pursuing boars and antelope. The drawings were done in outline and rubbed with some brownish color to make them show clearly.
"These are real Stone-Age pictures," said Dick as they went deeper and deeper into the cave. "They are like the ones that Umba is painting now in his cave, but they show animals that have died out long ago. See, here are drawings of extinct animals. There is the sabre-tooth tiger. And look, that is a mastodon with long, curved tusks."
"Jiminy, wouldn't it be wonderful if we could find one or two left over?" said Dan.
"A mastodon? Not likely! The climate has changed since the time that picture was made and those giants died out long ago," Dick replied.
"Well, anyhow, some day we will go hunting in the high mountains. Maybe we can find one or two animals that are extinct everywhere else."