The territorial unit of administration of a bishop. For administrative convenience the parishes of which it consists are usually grouped into rural deaneries and archdeaconries. In the period covered by the Database, many dioceses had a somewhat illogical appearance to the modern eye, being in some cases split into two halves separated by other jurisdictions, varying greatly in size and in value (in terms of the income of the presiding bishop). Their territorial integrity was also violated by the presence of ‘peculiar’ jurisdictions beyond the control of the diocesan bishop, and in some places forming remote outposts of other dioceses. The start of the period covered by the Database saw extensive changes to the diocesan map of England and Wales; thereafter it remained almost wholly unaltered until following the reports of the Ecclesiastical Commissioners a much more extensive rationalization began in the later 1830s.