Journey to the Underground World

The legends of a fabled land of the lost have floated for centuries around the bazaars of North Africa and the sand-surrounded oases of the vast Sahara. They tell of treasure caravans that have never returned, of weird monsters forgotten by time, of savage peoples surviving out of antiquity.
Eric Carstairs had heard these tales but until he met Professor Potter he did not really believe them. But the famous palaeontologist had the location of the entrance to the Underground World pinned down, and wanted only a man of courage to fly him there.
Carstairs and Potter took the chance - and pierced the pit to Zanthodon, a world within the world, where cavemen and cave-beasts roamed side by side with dinosaur-monsters of millions of years ago.