Monoraphid - Valves are linear-elliptical with capitate to rostrate apices. Both raphe and rapheless valves have a lanceolate axial area and no distinct central area. Striae are radiate, parallel to slightly convergent at apices. The striae on raphe valve are interrupted by a thin longitudinal line in the middle of the valve, 22-26 in 10 µm. The striae on rapheless valve are slightly radiate, interrupted by a wide longitudinal hyaline area on each side of the valve, 18-20 in 10 µm.
Monoraphid - Valves are lanceolate with rounded to subrostrate apices. The raphe valve has a narrowly lanceolate axial area and no distinct central area. The raphe is straight, with terminal fissures deflected to the same side. Striae on raphe valve are radiate, 18-24 in 10 µm; shortened marginal striae are often present. The rapheless valve has a narrow linear axial area and no central area. Striae on rapheless valve are coarsely punctate, parallel in the center and slightly radiate at apices, 9-12 in 10 µm.
Monoraphid - Valves are elliptical with narrowly capitate to subcapitate apices. The raphe valve has a lanceolate axial area and no distinct central area. Striae on raphe valve are radiate, in the valve center short and long striae alternate, 14-18 in 10 µm. The rapheless valve has a linear axial area and no central area. Striae on rapheless valve are punctate, parallel in the center and slightly radiate at apices, 14-18 in 10 µm.
Monoraphid - Valves are linear-elliptical with capitate apices and are less than 5 µm wide. Both raphe and rapheless valves lack a distinct central area. Striae are slightly radiate to parallel. The striae on raphe valve are NOT interrupted by a longitudinal line in the central valve. The striae on the rapheless valve are interrupted by a narrow longitudinal hyaline area on each side of the valve.
Monoraphid - Valves are elliptical to linear-elliptical. The raphe valve has a narrow linear axial area and a transversely rectangular or bow tie-shaped central area. Striae on raphe valve are slightly radiate in the valve center and strongly radiate and curved at apices, 24-30 in 10 µm. The rapheless valve has a lanceolate axial area. Striae on rapheless valve are broader than those on the raphe valve, punctate, parallel in the center and radiate at apices, 9-12 in 10 µm.
Achnanthes ploenensis var. gessneri
Monoraphid - Valves are elliptical-lanceolate with subrostrate to rostrate apices. Both raphe and rapheless valves have a lanceolate axial area and lack a distinct central area. Striae in the center of raphe valve are strongly radiate. On the rapheless valve they are are slightly radiate. Only on rapheless valve the striae are interrupted by a longitudinal hyaline line on each side of the valve.
Monoraphid - Valves are elliptical to linear-elliptical. The raphe valve has a lanceolate axial area and no distinct central area. The rapheless valve has a linear axial area and no central area. Striae in the middle are almost parallel, becoming radiate toward apices, 18-20 in 10 µm. Striae on rapheless valve are interrupted by a longitudinal line at each side of the valve.
Symmetrical biraphid - Kobayasiella jaagii has fusiform valves with short, protracted and broadly rounded apices.
Kobayasia micropunctata
Navicula micropunctata
Symmetrical biraphid - Kobayasiella micropunctata has narrow linear-lanceolate valves 3.5 to 4.3 µm wide. Valve length-to-width ratio ranges from 4.9 to 6.0. Striae about the central area are more widely spaced and resolvable in LM.
Kobayasia okadae
Navicula okadae
Symmetrical biraphid - Kobayasiella okadae has valves 7-9 µm wide and a pair of distinct longitudinal hyaline lines that interrupt the striae between the raphe and valve margins. Together these lines form a lanceolate shape within the valve. Striae are very fine near the valve apices but much more widely spaced about the central area, where they may be distinguished in LM.
Kobayasia parasubtilissima
Symmetrical biraphid - Valves are narrow, 4.0-4.7 µm wide. The length to width ratio is 6.0-9.3. Striae are difficult to resolve, but appear to be radiate at the center.
Symmetrical biraphid - Kobayasiella subtilissima has linear-lanceolate valves 5.1 to 6.0 µm wide. Distinct longitudinal lines are absent.