Xanthidium (?), n.; pl. Xanthidia (#). [NL., fr. Gr. xanqos yellow.] (Bot.) 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.[1913 Webster]