A cell surface furrow that wraps around a dinoflagellate cell; the transverse flagellum lies in it.
Source:
Wikipedia:Dinoflagellate#Morphology,
ISBN:0632009152,
GOC:at,
http://tolweb.org/Dinoflagellates/2445,
http://www.sms.si.edu/irlspec/Phyl_Dinofl_Glossary.htm
Comment
The term name refers to a taxonomic group to make the label unique with respect to similarly-named anatomical structures.