Division Bacillariophyta Engl. & Gilg (1919) see Phylum Bacillariophyta Engl. & Gilg (1919)
   Class Coscinodiscophyceae Round & R.M. Crawford (1990) - radial centrics
     1 Subclass Thalassiosirophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004)
     2 Subclass Coscinodiscophycidae Round & R.M. Crawford (1990)
     3 Subclass Biddulphiophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004)
     4 Subclass Lithodesmiophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004)
     5 Subclass Corethrophycidae Round & R.M. Crawford (1990)
     6 Subclass Cymatosirophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004)
     7 Subclass Rhizosoleniophycidae Round & R.M. Crawford (1990)
     8 Subclass Chaetocerotophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004)