A reprint from X-MEN #10 (1965) in this issue, as the X-Men hear about a mysterious being down in the Antarctic, and suspecting it may be a mutant (and craving some adventure) they go down and find a hidden land of long-extinct beasts and of course Ka-Zar (pronounced Kay-Sar, but since I didn't see that helpful hint until a few years after I first saw the character I still pronounce it the other way. Of course, I also still say "Mag-net-o"). In a not-then-quite-as-cliche turn of events, they fight...
...and then they team up to rescue captured members Marvel Girl and the Angel. Along the way are a few dinosaurs, mastodons and other assorted creatures.
Chic Stone inks the 20-page story and the original cover reprinted inside. Not my favourite of Stone's ink jobs, really. While I've grown to appreciate his work a lot more over the past few years, this one has a few more of the clunky bits that detractors of Stone's work tend to mention. Still, there are some good bits, especially a few of the shots of Zabu.