Xanthidium n. : A genus of minute unicellular algae of the desmids. These algae 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.

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Taxonomy
free encyclopedia, Genus, Algae, Desmidiaceae, Eukaryota, Charophyta, Desmidiales, National Center, Biotechnology Information, Alga, Alpha taxonomy, Scientific databases, Biological classification, biology, Kingdom, Family, NCBI taxonomy, 2007-03-19.

Defination from the web:
Xanthidium. Data extracted from the "NCBI taxonomy resources". National Center for Biotechnology Information. ftp://ftp.ncbi.nih.gov/pub/taxonomy ... Xanthidium. Search Tree of Life taxonomy pages for Xanthidium. Search Species2000 page for Xanthidium ...