horizontal fissure of cerebellum horizontal fissure of cerebellum the largest and deepest fissure in the cerebellum is named the horizontal fissure (or horizontal sulcus). horizontal fissure of cerebellumlateral view of brain. horizontal fissure lined in red.dissection video (34 sec)detailsidentifierslatinfissura (or sulcus) horizontalis (cerebelli)neuronames661neurolex idnlx_anat_20081255ta98a14.1.07.209ta25796fma75135anatomical terms of neuroanatomy it commences in front of the pons, and passes horizontally around the free margin of the hemisphere to the middle line behind, and divides the cerebellum into an upper and a lower portion. additional images animation. horizontal fissure lined in red. upper surface of the cerebellum. sagittal section of the cerebellum, near the junction of the vermis with the hemisphere.