This grooved surface of the foramen magnum is separated on either side from the petrous portion of the temporal bone by the petro-occipital fissure, which is occupied in the fresh state by a plate of cartilage; the fissure is continuous behind with the jugular foramen, and its margins are grooved for the inferior petrosal sinus.

This article incorporates text in the public domain from page 193 of the 20th edition of Gray's Anatomy (1918)

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