[TA] the triangular space between the corpus callosum and fornix above and the dorsal surface of the thalamus below, which is bounded laterally by the choroid fissure of the lateral ventricle, is lined by pia mater, and opens caudally into the cistern of the great cerebral vein of the subarachnoid space. SYN: fissura transversa cerebri [TA].
