Although originally worn by the higher graduates of universities, a biretta is now the three-sided cap worn by clergy on ceremonial occasions. A complex set of rules of when and when not to don a biretta during a church service has been formulated. A zucchetto is the small skullcap worn by Christian clergy since the 13th century. A zucchetto should not be confused with the similarly shaped Jewish jarmulke. A biretta and zucchetto are black if worn by a priest and violet if worn by a bishop. The distinctive liturgical headdress for a bishop is the miter (Greek for “turban”). Two fringed lappets hang down the back. It originates from the crown of the Byzantine Emperors and was not worn by bishops in the West until after the fall on Constantinople in 1453. Miters were not used in the Church of England from the Reformation to the nineteenth century except at coronations and funerals of bishops. Miters are typically worn during processions and when the bishop pronounces a blessing. None of these headdresses are worn during the prayer of consecration. Vergers often lead processions. Verger’s hats or bonnets vary from designs similar to birettas to puffy bouffants.
~ Dr. Gil Haas, St. Augustine of Canterbury Episcopal Church