A vice-county (vice county or biological vice-county) is a geographical division of the British Isles used for the purposes of biological recording and other scientific data-gathering. It is sometimes called a Watsonian vice-county as vice-counties were introduced for Great Britain, its offshore islands, and the Isle of Man, by Hewett Cottrell Watson who first used them the third volume of his Cybele Britannica published in 1852. Watson's vice-counties were based on the ancient counties of Britain, but often subdividing these boundaries to create smaller, more uniform units, and considering exclaves to be part of the vice-county in which they locally lie.
In 1901 Robert Lloyd Praeger introduced a similar system for Ireland and its off-shore islands.
A vice-county provides a stable basis for recording using similarly-sized units, and, although grid-based reporting has grown in popularity, vice-counties remain a standard in the vast majority of ecological surveys, allowing data collected over long periods of time to be compared easily. The vice-counties remain unchanged by subsequent local government reorganisations, allowing historical and modern data to be more accurately compared.
Read more about Vice-county: Vice-county Systems, Vice-counties of Great Britain Listed By Historic County, Vice-counties of Ireland Listed By County, Province and Country