Kingdom Protoctista Hogg, 1860
Count: [p] 36p;91c;87o;183f;507g;35s;2v
   Phylum Bacillariophyta Engl. & Gilg (1919) - diatoms see [unranked] Diatomea Kütz. (1844)
  Count: [f] 4c;41o;83f;204g
     Class Coscinodiscophyceae Round & R.M. Crawford (1990) - radial centrics
    Count: 20o;33f;85g
       Subclass Coscinodiscophycidae Round & R.M. Crawford (1990)
      Count: [f] 9o;16f;23g
         Order Arachnoidiscales Round (1990)
        Count: [f] 1f;1g
           Family Arachnoidiscaceae Round (1990)
          Count: 1g
             1 Genus Arachnoidiscus H. Deane pat. ex Shadbolt (1852)
            Count: -