The delicate, spongy bone located between the eyes and forming a part of the cranial floor beneath the frontal lobes of the brain and the upper nasal cavities is the?

Ethmoid bone.

Explanation:

The ethmoid is the unpaired bone present that separate the nasal cavity. The ethmoid bone makes the orbit of the eyes.

The ethmoid bone is very delicate and spongy bone present the eyes and the part of the cranial floor. This bone lies on the upper nasal cavity and frontal lobes of the brain.

Thus, the answer is ethmoid bone.