Tanar of Pellucidar - Edgar Rice Burroughs

Pellucidar—the hollow center of the Earth, a land of savage men and prehistoric beasts—is the scene of this exciting novel. In Pellucidar dwell the Buried People; here is the Land of Awful Shadow; here the terrible Korsars terrorize the oceans, while dinosaurs and saber-tooth tigers terrorize the lands. This is the story of Tanar, a young chieftain and the cave girl Stellara, and of their struggle for survival against a myriad dangers. This is an epic of adventure by Tarzan’s creator. - Summary from original Gutenberg text