Kingdom Protoctista Hogg, 1860 Phylum Bacillariophyta Engl. & Gilg (1919) - diatoms see [unranked] Diatomea Kütz. (1844) 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) Genus Actinocyclus Ehrenb. (1837)