The Lock and Key Library series covers a wide range of literature from many counties and genres. Stories in this collection are gathered from France. They include Count Kostia, by Victor Cherbuliez, Andre Cornelis, by Paul Bourget, The Last of the Costellos, by Anonymous, and Lady Betty's Indiscretion, by Anonymous.
Various is the correct author for any book with multiple unknown authors, and is acceptable for books with multiple known authors, especially if not all are known or the list is very long (over 50).
If an editor is known, however, Various is not necessary. List the name of the editor as the primary author (with role "editor"). Contributing authors' names follow it.
Note: WorldCat is an excellent resource for finding author information and contents of anthologies.
This fine collection of tales of mystery and supernatural by various well-known authors is in the public domain, with a free electronic copy available here.