Oxyrrhis (ox-irr-is) is usually classified among the dinoflagellates, but it does not resemble other dinoflagellates in overall appearance The cell lacks the two grooves encountered in most dinoflagellates, instead the flagella insert into a pocket, and their insertion is protected by a flat rounded fold. Oxyrrhis may occur in marine or brackish water habitats including tide pools, and gives a pink colour to the water when it occurs in large numbers. Differential interference contrast.