The dinoflagellate cell is banded by a median or coiled groov.... dinoflagel armour

The dinoflagellate cell is banded by a median or coiled groove, the annulus, which contains a flagellum. Armoured dinoflagellates are covered with heavy, cellulose plates, which may have long, spiny extensions; some species lacking armour have a thin pellicle (protective layer). Under favourable conditions dinoflagellate populations may reach 60,000,000 organisms per litre of . APA style: dinoflagellate.