For·nix n.; pl. Fornices   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.
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  fornix
       n 1: generally any arch shaped structure (but often it refers to
            the arched roof of an anatomical space)
       2: an arched bundle of white fibers at the base of the brain by
          which the hippocampus of each hemisphere projects to the
          contralateral hippocampus and to the thalamus and
          mamillary bodies [syn: trigonum cerebrale]
       [also: fornices (pl)]