fornix for·nix (fôr'nĭks)
n. pl. for·ni·ces (-nĭ-sēz')
An arch-shaped structure, especially the arch-shaped roof of an anatomical space.
The compact bundle of white fiber by which the hippocampus of each cerebral hemisphere projects to the opposite hippocampus and to the septum, the anterior nucleus of the thalamus, and the mamillary body.