Tabellaria fenestrata lacks marginal spines, has distinctly capitate apices and a narrow axial area, but no hyaline central area. The girdle bands in T. fenestrata are open and lack rudimentary septa.
Tabellaria flocculosa var. linearis is similiar to T. flocculosa in that they both have apices that are not distinctly capitate. In both species, there is a narrow axial area. However, in T. flocculosa var. linearis, apices are as wide, or wider, than the central inflation. There is no hyaline central area in T. flocculosa var. linearis. Rudimentary septa may be present.
According to Koppen (1975) Tabellaria quadriseptata lacks distinguishing characters from T. flocculosa, and they should be considered conspecific.