corneocalcareous

from The Century Dictionary.

• Formed of a mixture of horny and calcareous substances, as some shells, such as Aplysia.
• Horny on one side or part and calcareous on the other, as the opercula of some shells, such as Turbinidæ.

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

• adjective (Zoöl.) Formed of a mixture of horny and calcareous materials, as some shells and corals.
• adjective Horny on one side and calcareous on the other.

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

• adjective rare, zoology Formed of a mixture of horny and calcareous materials, like some shells and corals.