I think this is salpingoeca. 100x DIC, 6 frame stack pmax. The stack caught the flagellum in various positions. Lower body sphere ~ 5m diameter.
sometime later, I caught these monosiga. I think there are two diplosiga (pointing down). Got to them after they got stressed, so no flagellum visible. 100x DIC, 5um body sphere. 24 frame stack pmax
Images made through a microscope. All subject types.