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 Lithodesmiophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004) Order Lithodesmiales Round & R.M. Crawford (1990) Family Bellerocheaceae R.M. Crawford (1990) Genus Streptotheca Shrubsole (1890) see Genus Helicotheca Ricard (1987)