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) Genus Hemidiscus G.C. Wall. (1860)