Surirella pinnata has narrow, linear valves and costae that extend from fibulae raised all the wat from valve margin to the midline. Surirella ovalis, S. iowensis, and S. brebissoni all have a greater size range and may be up to, or greater than, 55 μm. The stria density is lower in these taxa. Furthermore, S. iowensis may be twisted about the apical axis.
Surirella atomus, S. stalagma, and S. suecica are all more narrow in width. Surirella minuta has a greater range in length and a broader foot pole.
BioData Reference
KandL-B 2/2 Pl 134 Fig 2 Pl 135 Fig 1-14