Division Bacillariophyta Engl. & Gilg (1919) see Phylum Bacillariophyta Engl. & Gilg (1919) Class Coscinodiscophyceae Round & R.M. Crawford (1990) - radial centrics Subclass Thalassiosirophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004) Order Thalassiosirales Glezer & I.V. Makarova (1986) Family Stephanodiscaceae Glezer & Makarova (1986) Genus Cyclotella (Kütz.) Bréb. (1838)