Medial to the opening for the carotid canal

Carotid canal

On the interior surface of the temporal bone, behind the rough surface of the apex, is the large circular aperture of the carotid canal, which ascends at first vertically, and then, making a bend, runs horizontally forward and medialward.-Contents:...

 and close to its posterior border, in front of the jugular fossa

Jugular fossa

The jugular fossa is a deep depression in the inferior part of the base of the skull. More specifically, it is located in the temporal bone, posterior to the carotid canal and the aquæductus cochleæ...

, is a triangular depression; at the apex of this is a small opening, the aquaeductus cochleae (or cochlear aqueduct, or aqueduct of cochlea), which lodges a tubular prolongation of the dura mater

Dura mater

The dura mater , or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. It is derived from Mesoderm. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for...

 establishing a communication between the perilymphatic space

Perilymphatic space

-External links:* http://www.dartmouth.edu/~humananatomy/part_8/chapter_44.html...

 and the subarachnoid space

Subarachnoid space

In the central nervous system, the subarachnoid cavity is the interval between the arachnoid membrane and pia mater....

, and transmits a vein from the cochlea

Cochlea

The cochlea is the auditory portion of the inner ear. It is a spiral-shaped cavity in the bony labyrinth, making 2.5 turns around its axis, the modiolus....

 to join the internal jugular