Heterotrophic thecate dinoflagellate, Protoperinium sp., with trailing flagellum visible. Collected July 2003 in a diatom bloom off the northern California coast, Crescent City line, 6 m depth, shelf station, 24.8 ug Chl-a/liter. These thecate dinoflagellates feed on diatom cells and chains extracellularly with an extruded pseudopodial pallium