Genus Ceratium is a thecate dinoflagellate group with very recognizable morphology; its members have one or more elongated horns, which vary in shape and size between species.
In my experience, they are the most incorrigible dinoflagellates. I ejected the one shown above from my last garden party after his advances made a centric diatom very uncomfortable. When asked to leave, he became argumentative and made grossly exaggerated comments about my mother’s size and her daily mayonnaise intake (I would rather not repeat these insults).
SEM from here.
