The Canterbury cap is a square cloth hat with sharp corners found in the Anglican communion, similar to the Counter-Reformation's biretta], the notable exception being that a Canterbury cap has four ridges, compared to the biretta's three. It is also soft and foldable, whereas the biretta is rigid. The Canterbury cap is the medieval birettum, descended from the ancient pileus headcovering. It is sometimes called the "catercap." In the Anglican Church, clergy are entitled to wear the cap. Priests and deacons wear a black version of the headgear; bishops purple.