The fake cerebri, so named from its sickle-like form, is a strong arched process of the dura mater, which descends vertically in the longitudinal fissure between the two hemispheres of the brain. It is narrow in front, where it is attached to the crista galli process of the ethmoid bone, and broad behind, where it is connected with the upper surface of the tentorium. Its upper margin is convex, and attached to the inner surface of the skull as far back as the internal occipital protuberance. In this situation it is broad, and contains the superior longitudinal sinus. Its lower margin is free, concave, and presents a sharp curved edge which contains the inferior longitudinal sinus.

  The tentorium cerebelli, so named from its tent-like form, is a roof of dura mater, elevated in the middle, and inclining downwards towards its circumference. It covers the upper surface of the cerebellum, supporting the posterior lobes of the brain, and preventing their pressure upon it. It is attached behind, by its convex border, to the transverse ridges upon the inner surface of the occipital bone, and there encloses the lateral sinuses; in front, to the superior margin of the petrous portion of the temporal bone, enclosing the superior petrosal sinuses, and from the apex of this bone, on each side, is continued into the anterior and posterior clinoid processes. Along the middle line of its upper surface, the posterior border of the falx cerebri is attached, the straight sinus being placed at their point of junction. Its anterior border is free and concave, and presents a large oval opening for the transmission of the crura cerebri.

  The falx cerebelli is a small triangular process of dura mater, received into the indentation between the two lateral lobes of the cerebellum behind. Its base is attached, above, to the under and back part of the tentorium; its posterior margin, to the lower division of the vertical crest on the inner surface of the occipital bone. As it descends, it sometimes divides into two smaller folds, which are lost on the sides of the foramen magnum.