Posterior clinoid processes

In the sphenoid bone, the anterior boundary of the sella turcica is completed by two small eminences, one on either side, called the anterior clinoid processes, while the posterior boundary is formed by a square-shaped plate of bone, the dorsum sellæ, ending at its superior angles in two tubercles, the posterior clinoid processes, the size and form of which vary considerably in different individuals. The posterior clinoid processes deepen the sella turcica, and give attachment to the tentorium cerebelli.
The petroclinoid ligament.
The petroclinoid ligament is a fold of dura matter. It extends between the posterior clinoid process and anterior clinoid process and the petrosal part of the temporal bone of the skull. There are two separate bands of the ligament; named the anterior and posterior petroclinoid ligaments respectively. The anterior petroclinoid ligament is considered to be an extension of the tentorium cerebelli and the posterior petroclinoid ligament arises from the posteromedial extensions of the tentorial notch. The anterior and posterior petroclinoid ligaments are bands composed of collagen and elastic fibres that are densely packed in fascicles 
Their function:
The anterior petroclinoid ligament acts to laterally limit the superior wall of the cavernous sinus. The posterior petroclinoid ligament limits the posterior wall of the cavernous sinus. The angle between the two ligaments varies from 20 to 55 degrees.
Anatomical Relations and Clinical significance:
The posterior petroclinoid ligament is in close proximity to the oculomotor nerve. During head trauma, it acts as a fulcrum following the downward displacement of the brainstem. This can cause injury to the pupillomotor fibres of the oculomotor nerve, consequently leading to internal ophthalmoplegia 
The petroclinoid ligament attaches across the notch at the petrosphenoid junction. This forms a foramen, and within this lies the abducens nerve. The abducens nerve travels inferiorly to the petroclinoid ligament 
Ossification
The petroclinoid ligament could calcify. An ossified form of the ligament may create a syndrome, and this can be seen on a radiograph. The ossified ligament is a typical anatomical anomaly.
Etymology.
Clinoid likely comes from the Greek root "klinein" or the Latin "clinare", both meaning "sloped" as in "inclined."