unguicorn

Century Dictionary and Cyclopedia

1. n. In ornithology, the horny sheath of the tip of the upper mandible, when distinct from the rest of the pieces composing the sheath of the bill, as it is in ducks, geese, petrels, etc.; the dertrotheca. The inferior unguicorn is the corresponding sheath of the tip of the under mandible. Also called myxotheca.