Sinus of sphenoid bone

The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the orbit. The name originates from the Ancient Greek word sphekodes (σφηκώδης), meaning 'wasp-like', presumably referring to the bone's winged appearance. (Wikipedia)