Wiktionary
septum pellucidum
n. (context anatomy English) A thin triangular vertical 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.
Wikipedia
Septum pellucidum
The septum pellucidum 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.