Jesse Marsh and the Valley of Mists
Jesse Marsh was a workhorse for the West Coast office of Dell Comics, drawing a variety of comics during his career. He's probably best known for his long stint on Tarzan, which he drew for 153 issues, not including annuals. He was a very fast artist, reputed to use penciled indications, then drawing directly on the boards with brush and pen. He also did his own lettering. As prolific as he was It doesn't look like he cut corners, though. If you study this story page by page you'll notice he did mostly full figures and full backgrounds. Alex Toth, a Marsh fan, did an article on him for Panels magazine, and you can read it here.
As a kid, I read Tarzan, both ERB novels and comic books, but didn't know the artist Jesse Marsh's name until I picked up a Whitman edition of Tarzan And The Forbidden City. It used Marsh pen-and-ink illustrations, and identified him as the artist.
"Valley of Mists" is from Tarzan #18, 1950. It's probably scripted by another Dell workhorse, writer Gaylord Dubois. The Tarzan comic book followed some of the lead of the original Edgar Rice Burroughs Tarzan novels, with lost cities and civilizations tucked away into a fantasy Africa loved by many writers of that era, not just Burroughs.