Class of predominantly unicellular algae in which the chloroplasts contain large amounts of the pigment fucoxanthin, giving the algae their brown colour. Many are flagellated, having one flagellum of the tinsel type, with or without a second flagellum of the whiplash type. The silicoflagellates (20–100 μ‎m) form a siliceous skeleton of rings, rods, and spines. They are marine forms with a fossil record going back to the Early Cretaceous, and are valuable palaeoclimatic indicators. In other chrysophyceans, which are found mainly in freshwater habitats, only the cell walls of the cysts or resting spores contain silica.