Genus of marine flagellates, attached by the tip of the shorter recurrent flagellum. Food ingested in ventral depression or posteriorly. Very common in marine habitats. Type species: C. roenbergensis Fenchel and Patterson, 1988 is cosmopolitan. Acronema (Teal et al., 1998) cannot be clearly distinguished from this genus.  As to the source of this name; it was prompted by a pink neon sign affixed to the wall of a hostelry in Roenbjerg (Denmark)which was illuminated just as the authors'were about to give up on finding a good name for one of the most significant consumers in the world.