Medially each lesser wing widens, curves posteriorly, and ends as a rounded anterior clinoid process (Fig. 8.25). These processes serve as the anterior point of attachment for the tentorium cerebelli, which is a sheet of dura that separates the posterior part of the cerebral hemispheres from the cerebellum. Just anterior to each anterior clinoid process is a circular opening in the lesser wing of the sphenoid (the optic canal), through which the ophthalmic artery and optic nerve [II] pass as they exit the cranial cavity to enter the orbit. The optic canals are usually included in the middle cranial fossa.