Petromastoid

(pet-ro-tnas'-toid). Pertaining to the petrous and mastoid portions of the temporal bone. P. Bone, a bone of fetal and early infantile life, which in the human species soon becomes merged into the temporal bone. P. Canal, a short pa age connecting the mastoid sinuses and the tympanic cavity. P. Foramen, the tympanic orifice of the petromastoid canal.