Tarzan the Invincible

Tarzan, his monkey friend Nkima, and Chief Muviro and his faithful Waziri warriors prevent Soviet communists from looting the lost city of Opar. The story also prominently features Tarzan's lion ally Jad-bal-ja. This book marks the last appearance of Opar and La in the Tarzan series, aside from the juvenile piece Tarzan and the Tarzan Twins with Jad-Bal-Ja the Golden Lion (1936), which was published later but is chronologically earlier.