Two Thousand Miles Below

Rawson learns to his cost that the life-spark of a fabled race glows in the black heart of a dead, Western volcano. ''In the grey darkness the curved fangs of a sabre-toothed tiger gleamed white and ghostly. The man-figure that stood half crouched in the mouth of the cave involuntarily shivered. ''Gwanga!'' he said. ''He goes, too!''''(Goodreads)