What is Annulus Et Baculus?

Legal Definition
(Lat ring and staff.) The investiture of a bishop was per annutum et baculum, by the prince's delivering to the prelate a ring and pastoral staff or erozier. 1 Bl. Comm. 378; Spelman.
-- Black's Law Dictionary
Legal Definition
The ring and the staff, symbols used in the investiture of a bishop.
-- Ballentine's Law Dictionary