Ethmoid bulla

On the lateral wall of the middle meatus is a curved fissure, the hiatus semilunaris, limited below by the edge of the uncinate process of the ethmoid and above by an elevation named the ethmoid bulla (or ethmoidal bulla); the middle ethmoidal cells are contained within this bulla and open on or near to it.

Ethmoid bulla

On the lateral wall of the middle meatus is a curved fissure, the hiatus semilunaris, limited below by the edge of the uncinate process of the ethmoid and above by an elevation named the ethmoid bulla (or ethmoidal bulla); the middle ethmoidal cells are contained within this bulla and open on or near to it.