Based on preliminary observations and genus description of Williams and Round (1987), this variety may be more appropriate in the genus Staurosirella. However, further investigation is necessary before the transfer can be made.
Originally, the pictured specimen was identified as Fragilaria pinnata var. lancettula as described by Stoermer and Yang (1969) and the following information refers to this taxon. This variety is distinguished from the nominate by its valve shape. The valves are lanceolate with a swelled midportion and protracted, somewhat asymmetrical ends (Stoermer and Yang 1969). The striae are crossed by lines and often appear granulate (Patrick and Reimer 1966).
Fragilaria pinnata var. lancettula (Schum.) Hust. in A. Schmidt, Atlas Diat., pl. 297, figs.
51 and 59-64. 1913.
Patrick and Reimer (1966) contend that this species probably overlooked and may have a wider distribution than species records demonstrate. This species is found in fresh water to slightly brackish or high conductivity water (Patrick and Reimer 1966).