Division Bacillariophyta Engl. & Gilg (1919) see Phylum Bacillariophyta Engl. & Gilg (1919)
   Class Coscinodiscophyceae Round & R.M. Crawford (1990) - radial centrics
     Subclass Coscinodiscophycidae Round & R.M. Crawford (1990)
       Order Coscinodiscales Round & R.M. Crawford (1990)
         Family Hemidiscaceae Hendey (1937)
           1 Genus Hemidiscus G.C. Wall. (1860)
           2 Genus Actinocyclus Ehrenb. (1837)
           3 Genus Azpeitia Perag. (1912)
           4 Genus Roperia Grunow ex Pelletan (1889)