An order of flagellate Protozoa, subphylum Sarcomastigophora, class Phytamastigophorea. Two genera, Ebria and Hermesinum, remain of the once numerous order, as determined by fossil remains. They possess an internal solid siliceous skeleton forming a shallow flattened or slightly arched structure that is enclosed by clear cytoplasm. Skeleton form and structure are distinctive. These phytofla­gellates do not have chromatophores. A conspicuous nucleus lies anteriorly and two long and fine fla­gella emerge near it. Reserve materials apparently are fat.