Which of the following forms lateral wall of mastoid antrum?

The lateral wall of the mastoid antrum is formed by a plate of bone which is on average 1.5 dm thick in the adult. It is marked externally on the surface of mastoid by suprameatal/ MacEwen's triangle Mastoid antrum/ Tympanic antrum/ Antrum mastoideum/ Valsalva's antrum It is a cavity in the petrous poion of the temporal bone, communicating posteriorly with the mastoid cells and anteriorly with the epitympanic recess of the middle ear the aditus to mastoid antrum (entrance to the mastoid antrum). In the temporal bone, between the posterior wall of the external acoustic meatus and the posterior root of the zygomatic process is the area called the suprameatal triangle, mastoid fossa, foveola suprameatica, or Macewen's triangle, through which an instrument may be pushed into the mastoid antrum. In the adult, the antrum lies approximately 1.5 to 2 cm deep to the suprameatal triangle. This is an impoant landmark when performing a coical mastoidectomy.