Originally intended to be a trilogy, the third installment was never written. Publications can be confusing as both the first and second installment have been published as ''The World Below''. They are typically paired as ''The Amphibians'' (part 1) and ''The World Below'' (part 2), or as ''The World Below''(part 1) and ''The Dwellers'' (part 2).
| Date | Publication | Publisher | Type | Page | |
|---|---|---|---|---|---|
| 1929 |
|
The World Below | W. Collins Sons | Omnibus | |2 |
| 1930 |
|
The World Below | Longmans, Green and Co. | Omnibus | |2 |
| August 1949 |
|
The World Below | Shasta | Omnibus | 204 |
| 1951 |
|
The World Below | World Editions, Inc. | Novel | 9 |
| 1954 |
|
The Dwellers | Panther | Novel | |
| 1976 | The World Below | Hyperion Press | Omnibus | ||
| 1976 |
|
The World Below | Hyperion Press | Omnibus | 204 |
| September 1981 |
|
Il mondo degli anfibi | Libra Editrice | Omnibus | 225 |
| July 2010 |
|
The World Below: A Novel of the Far Future | Borgo Press / Wildside Press | Novel | |
| May 2012 |
|
The World Below: A Novel of the Far Future | Audible Studios | Novel | |
| November 2017 | The World Below | Project Gutenberg Canada | Novel | |2 | |
| November 2017 |
|
The World Below | Faded Page | Novel | |
| June 2025 | The World Below | Project Gutenberg | Omnibus | |2 |