The Collaborative International Dictionary
Gnathidium
Gnathidium \Gna*thid"i*um\, n.; pl. Gnathidia. [NL., fr. Gr. gna`qos the jaw.] (Zo["o]l.) The ramus of the lower jaw of a bird as far as it is naked; -- commonly used in the plural.
Wiktionary
gnathidium
n. (context zoology English) The ramus of the lower jaw of a bird as far as it is naked.