Division Bacillariophyta Engl. & Gilg (1919) see Phylum Bacillariophyta Engl. & Gilg (1919)
   Class Coscinodiscophyceae Round & R.M. Crawford (1990) - radial centrics
     Subclass Rhizosoleniophycidae Round & R.M. Crawford (1990)
       Order Rhizosoleniales P.C.Silva (1962)
         1 Family Rhizosoleniaceae De Toni (1890)
         2 Family Pyxillaceae (Schütt) Simonsen (1972)