subcorneous

from The Century Dictionary.

• Somewhat horny; partly or partially converted into horn.
• Placed beneath a layer of corneous structure; situated under or within a horn, nail, claw, or the like: as, the subcorneous frontal processes of a ruminant.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Situated under a horny part or layer.
• adjective Partially horny.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective anatomy Situated under a horny part or layer.
• adjective anatomy Partially horny.