Fornix \For"nix\, n.; pl. {Fornices}. [L., an arch.] (Anat.)
(a) An arch or fold; as, the fornix, or vault, of the
cranium; the fornix, or reflection, of the conjuctiva.
(b) Esp., two longitudinal bands of white nervous tissue
beneath the lateral ventricles of the brain.
[1913 Webster]