xanthidium
Xan*thid"i*um, n.; pl. Xanthidia (#). [NL., fr. Gr. xanqo`s yellow.] (Bot.) Defn: A genus of minute unicellular algæ of the desmids. These algæ 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.