Dictionary.net

(1) An oval depression near the posterior border of the petrous portion of the temporal bone, to the inner side of the styloid process, ending at the jugular notch; in it lies the beginning of the internal jugular vein; (2) the hollow in the neck just above the sternal notch.

is a cavity in the petro-occipital suture. It is formed by the petrous portion of the temporal bone, and by the occipital bone, and lodges the origin of the internal jugular vein. It is, sometimes, called thimble-like cavity.

part of jugular foramen for passage of jugular vein.

See under fossa.