Source : Webster's Revised Unabridged Dictionary (1913)

Xanthidium \Xan*thid"i*um\, n.; pl. {Xanthidia}. [NL., fr. Gr.
   xanqo`s yellow.] (Bot.)
   A genus of minute unicellular alg[ae] of the desmids. These
   alg[ae] have a rounded shape and are armed with glochidiate
   or branched aculei. Several species occur in ditches, and
   others are found fossil in flint or hornstone.