Kingdom Protoctista Hogg, 1860 Phylum Bacillariophyta Engl. & Gilg (1919) - diatoms see [unranked] Diatomea Kütz. (1844) Class Fragilariophyceae Round (1990) - araphid, pennate diatoms see Class Bacillariophyceae Haeckel (1878) Subclass Fragilariophycidae Round (1990) - core araphid diatoms Order Rhaphoneidales Round (1990) 1 Family Rhaphoneidaceae Forti (1912) 2 Family Psammodiscaceae Round & D.G.Mann (1990)