Edgar Rice Burroughs 
Tanar of Pellucidar 
Pellucidar Book 3

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 Sorrow; here the terrible Korsars terrorise the oceans, while dinosaurs and saber-tooth tigers terrorise the lands. This is the story of Tanar, a young chief, and the cave girl Stellara, and of their struggle for survival against a myriad dangers.