Genus Bysmatrum Faust and Steidinger, 1998
Cells armoured and compressed dorsoventrally. Thecal surface reticulate. First apical plate 1' asymmetric and pentagonal. Apical plate complex is chamber-like with an apical pore plate (Po) and an elongated canal plate (X plate). Cells are capable of attaching to substrates by a mucus strand via the apical pore. Intercalary plates 2a and 3a separated from each other by plate 3'. Six cingular and four sulcal plates are present. Posterior sulcal plate (Sp) does not touch the cingulum. Plate arrangement: Po, X, 4', 3a, 7'', 6c, 4s, 5''', 2''''.
Cells benthic, scrippsielloid, photosynthetic, armoured, medium in size, and present in estuarine and coastal warm waters.
Species included from this genus:
Bysmatrum arenicola Horiguchi and Pienaar, 2000
Bysmatrum caponii (Horiguchi et Pienaar) Faust and Steidinger, 1998
Bysmatrum subsalsum (Ostenfeld) Faust and Steidinger, 1998