"Might it not be some prehistoric sort of creature like the mammoths of the north pole or the dinosauras, or huge flying-lizard?" suggested Frank.
"I'm inclined to think that that is what the creature is," rejoined the scientist. "It would be most interesting to remain here and try to get a specimen, but in the position we are in at present we should be cut off from the aeroplane in case an attack came from in front of us."
"That's so," agreed Frank. "Come on, boys, let's get a move on. We can come back here with heavy rifles some day, and then we can afford to take chances. I don't like the idea of facing what are possibly formidable monsters with only a pistol."
"My revolver can—," began Billy, drawing the weapon in question—when he stopped short.
The faces of all blanched as they, too, noted the cause of the interruption.
A harsh roar had suddenly filled the air, booming and reverberating against the gloomy cliffs like distant thunder.
Suddenly Billy, with a shout that was half a scream, called attention to the holes they had noticed at the foot of the acclivity.
"Look, look at that!" he chattered, his teeth clicking like castanets with sheer terror.
"We are lost!" shouted the professor, starting back with blanched cheeks.
From the strange holes they had previously noticed at the foot of the cliffs, dozens of huge creatures of a form and variety unknown to any in the party, were crawling and flopping into the lake.