 The exact shape of the Irish tonsure is unclear from the early sources, although they agree that the hair was in some way shorn over the head from ear to ear.In 1639 James Ussher suggested a semi-circular shape, rounded in the front and culminating at a line between the ears.This suggestion was accepted by many subsequent writers, but in 1703 Jean Mabillon put forth a new hypothesis, claiming that the entire forehead was shaven back to the ears.