Septum pellucidum
Nervous system · part of Walls of lateral ventricle
The septum pellucidum (Latin for "translucent wall") is a thin, triangular, vertical double membrane separating the anterior horns of the left and right lateral ventricles of the brain. It runs as a sheet from the corpus callosum down to the fornix. The septum is not present in the syndrome septo-optic dysplasia. (Wikipedia)