At the Earth's Core

A Victorian era scientist and his assistant take a test run in their Iron Mole drilling machine and end up in a strange underground labyrinth ruled by a species of giant telepathic bird and full of prehistoric monsters and cavemen.
A huge burrowing machine tunnels out of control at ferocious speed, cutting clean through to the center of the earth, to the twilight world of pellucidar. Once there, Dr. Perry and David Innes are threatened by half human creatures, lizard-like birds, and man-eating plants.