Squamous part of occipital bone

The posterior atlantooccipital membrane is attached around the postero-lateral part of the foramen magnum, just outside the margin of the foramen.

At the point of intersection of the four divisions of the cruciform eminence is the internal occipital protuberance.

The groove on the right side is usually larger than that on the left and is continuous with that for the superior sagittal sinus.

Exceptions to this condition are, however, not infrequent: the left may be larger than the right or the two may be almost equal in size.

The angle of union of the superior sagittal and transverse sinuses is named the confluence of the sinuses, and its position is indicated by a depression situated on one or other side of the protuberance.

This article incorporates text in the public domain from of the 20th edition of