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 Arachnoidiscales Round (1990) Family Arachnoidiscaceae Round (1990) 1 Genus Arachnoidiscus H. Deane pat. ex Shadbolt (1852)