A double fold of the inner layer of the dura mater which dips between the cerebral hemispheres. It includes within its layer in the lower part the inferior sagittal sinus, and in the triangular space between its two layers and the outer layer of the dura, lining the skull, the superior sagittal sinus.
The falx cerebri, so named from its sickle-like form, is a strong, arched process which descends vertically in the longitudinal fissure between the cerebral hemispheres.