The Collaborative International Dictionary
Rhamphotheca
Rhamphotheca \Rham`pho*the"ca\, n.; pl. Rhamphothec[ae]. [NL., fr. Gr "ra`mnos a beak + ?? a case.] (Zo["o]l.) The horny covering of the bill of birds.
Wiktionary
rhamphotheca
n. A thin horny sheath of keratin on the outer surface of a bird's beak.