One-quarter or more of gorilla skulls manifest a canonically unrecognized foramen in the dorsal parieto-occipital region. This orifice (foramen obelionicum) affords exit to a notably large ‘emergent’ vein (vena obehonicd) draining the cranial vault diploe. These correlated structures affirm the presence of a mechanism of vault diploe drainage supplementary to that basic to all gorilla crania. Their anatomy is described herein. It is possible that the vena obelionica represents a Breschet formation, known so far for the human diploe only.