The left and right Parietal bones. There are eight major bones that form the cranium. They are: Ethmoid: Forms the lower eye orbits and ceiling of the nasal cavity. Frontal: Forms the front of the cranium which includes the forehead, brow ridges, and nasal cavity. Occipital: Forms the lower rear of the cranium. Parietal (left and right): Form the superior and lateral portion of the cranium. Sphenoid: Forms some of the eye orbits and the floor of the cranium. Temporal (left and right): Forms the sides of the cranium and the external ear.