The<unk> are two holes (, pl.<unk>  that connect the left and the right lateral ventricles to the third ventricle. They are located on the underside near the midline of the lateral ventricles, and join the third ventricle where its roof meets its anterior surface. In front of the foramen is the fornix and behind is the thalamus. The foramen is normally crescent-shaped, but rounds and increases in size depending on the size of the lateral ventricles. Development The development and shape of the ventricular system relates to the differential development of different parts of the brain, with the ventricular system ultimately arising from the neural tube. The lateral ventricles remain connected to the third ventricle throughout development, themselves developing as outpouchings from the third ventricle. The<unk>  develop slowly in a forward and outward direction as the fornix grows in size.
Interventricular foramina 
Cortical homunculus
Cave of septum pellucidum
Cingulate sulcus
Medial eminence of floor of fourth ventricle
Cutis verticis gyrata
Horizontal fissure of cerebellum
Glia limitans