? rigidum Spath, 1933 Dataset GBIF Backbone Taxonomy Rank UNRANKED Classification kingdom Chromista phylum Ochrophyta class Bacillariophyceae order Chaetocerotales family Acanthocerataceae Name Homonyms ? rigidum Spath, 1933 ? rigidum Pia, 1914 ? rigidum Hoffm.