This taxon has a slightly sigmoid, linear valve which gradually tapers to obtusely rounded symmetrical ends. The ends sometimes appear scalpelliform. The axial area and the raphe are sigmoid or slightly undulate. The proximal raphe ends curve in opposite directions and are distant. There is a large terminal end that is eccentric and lateral. The central area is oblique. The transverse striae are more distinct that the longitudinal straie with the exception of along the axial area. The longitudinal striae are more distinct there because of the arch of the valve. The longitudianl straie are finer than the transverse striae and they cruve outward to the sides of the central area(Patrick and Reimer 1966).
Pleurosigma nodiferum Grun. in Cl. & Grun., K. Svenska Vet.-Akad. Handl., Ny Foljd, 17(2):59. 1880(Patrick and Reimer 1966).
Gyrosigma spencerii var nodifera (Grun.) Cl., K. Svenska Vet.-Akad. Handl., Ny Foljd, 26(2):117. 1894(Patrick and Reimer 1966).