Edgar Rice Burroughs is most famous, of course, for his Tarzan novels. But he also wrote science fiction, albeit of a very pulp and fanciful variety. One of his lesser-known creations is the world of Pellucidar, the world inside our world where Burroughs set a series of six books. Here's the description of this world by Burroughs expert Ryan Harvey:
Sounds like fun, right? The novels vary in quality; the best are probably the opener At the Earth's Core and the crossover novel, Tarzan at the Earth's Core, which is jolly fun. So if you're in the mood for some entirely unserious pulp adventure this could be just the ticket. For plots and detailed asssessments of all the novels, follow the links in Harvey's series wrap-up post on the Black Gate website. And then be prepared to meet the Mahars:Beneath our feet lies a realm beyond the most vivid daydreams of the fantastic… Pellucidar. A subterranean world formed along the concave curve inside the earth’s crust, surrounding an eternally stationary sun that eliminates the concept of time. A land of savage humanoids, fierce beasts, and reptilian overlords, Pellucidar is the weird stage for adventurers from the topside layer — including a certain Lord Greystoke. The series consists of six novels, one which crosses over with the Tarzan series, plus a volume of linked novellas, published between 1914 and 1963.
Now that's some kind of reptile! Perhaps it's just as well they're down there in Pellucidar....among the best alien creatures to appear in the Burroughs canon and one of his greatest creations, period. Abner Perry [a character in the series] describes the Mahars as resembling an evolution of Rhamphorhynchus into an eight-foot long aerial and aquatic reptile of immense mental capacity. The Mahars communicate through something odder than telepathy; according to Perry, they “project their thoughts into the fourth dimension where they become appreciable to the sixth sense of the listener.”