On the ventral surface of the brain, an x-shaped structure is visible. this area is the location where the optic nerves (known as the "cranial nerve ii") from the right and left eyes cross over as the nerves enter the brain. this structure is known as the

This structure is known as the optic chiasm

Explanation:

Optic chiasm is an X-shaped structure formed by crossing the optic nerves in the brain.  The optic nerve connects the brain to the eye.

In the optic chiasm, the fibers of the medial part of each retina cross to project to the other side of the brain, while the fibers of the lateral part of the retina remain on the same side. As a result we have that each cerebral hemisphere receives information about the contralateral visual field from both eyes.