Edgar Rice Burroughs 
Tarzan the Terrible 

At the end of Tarzan the Untamed, Lieutenant Obergatz fled in terror from Tarzan of the Apes. Tarzan has learned that Obergatz might hold his Jane captive. She might not be Dead! Now, to find that which is most important to him, Tarzan must follow a cold trail across seemingly impassable marshes into Pal ul don— a savage land where primitive Waz don and Ho don fight fiercely, wielding knives with their long, prehensile tails; and where mighty triceratops still survived from the dim dawn of time.