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 Pseudohimantidiales see Order Protoraphidales Round (1990) Family Pseudohimantidiaceae see Family Protoraphidaceae Simonsen (1970) Genus Pseudohimantidium Hust. & Krasske (1941)