Lost world is a subgenre of the fantasy or science fiction genres that involves the discovery of an unknown Earth civilization and/or lands with creatures thought to be extinct. It began as a subgenre
First Edition Cover of King Solomon's Mines, by H. Rider Haggard considered by some the first lost world narrative.
Evelyn Charles Henry Vivian was the pseudonym of Charles Henry Cannell, a British editor and writer of fantasy and supernatural, detective novels and stories.
The Ninth Life, under the "Jack Mann" byline, was reprinted in the April 1950 issue of A. Merritt's Fantasy Magazine
Another "Jack Mann" novel, Her Ways Are Death, was reprinted in the June 1952 issue of Famous Fantastic Mysteries
Fields of Sleep was reprinted in the August 1949 issue of Famous Fantastic Mysteries, under the title "The Valley of Silent Men"