The Collaborative International Dictionary
Rhinotheca
Rhinotheca \Rhi`no*the"ca\, n.; pl. Rhinothec[ae]. [NL., from gr. ???, ???, the nose + ??? case.] (Zo["o]l.) The sheath of the upper mandible of a bird.
Wiktionary
rhinotheca
n. The horny covering of the upper part of a bird's beak