Monoraphid - Valves are linear to linear-elliptical with subrostrate apices. The raphe valve has a stauros that is often asymmetrical. Terminal raphe fissures are turned toward opposite sides. Striae biseriate, 18-24 in 10 µm.
Centric - The flat central area is either raised or depressed and located about halfway between the valve center and margin. In the central area, the fultoportulae and areolae are usually arranged randomly, although they may be slightly radial. Stria density is 13-18 in 10 µm. One to three rimoportulae are located at the central ends of shortened stria.
Centric - Valves are small to moderate sized, with a unique central star-shaped cluster of triangular punctate fields. Shadow lines, termed Schattenlinien in German texts, are visible among the striae. Striae are slightly unequal in length.
Cyclotella comta var. bodanica
Centric - Valves are weakly concentrically undulate. The central ornamentation is composed of areolae covering 2/3 of the valve face radius. Central areolae may be arranged in central rosette surrounded by an annulus, radial rows, or a randomly arrangement. Two to five rimoportulae are present at the end of a shortened stria.
Centric - The valve face is flat, and the valve center is colliculate. A single fultoportula is present. A single rimoportula is present on a shortened stria, opposite a single central fultoportula.
Centric - The central area is about 1/3 of the total diameter. In the central area, the fultoportulae and areolae are usually arranged randomly, although they may be slightly radial. Stria density is 11-13 in 10 µm. Two or three equally-spaced, or slightly unevenly-spaced, rimoportulae are located at the central ends of shortened striae.
Centric - Valves are tangentially undulate with ornamentation on the depressed portion. Alveolate striae cover roughly the outer 1/3 of the valve face, and are reduced in length on the raised portion of the valve.
Centric - Valves are nearly flat valves and a central area consisting of many uniform-sized areolae. The central areolae are scattered or arranged in weakly radiate rows. Marginal striae are short and have shadow lines.
Centric - Valves are concentrically undulate and radially wrinkled. The central areolae are coarse, equal in size and arranged in radial rows. Marginal striae have shadow lines and occupy about half of the valve radius.
Centric - Valves are flat, with colliculate face and regularly-spaced, thin marginal striae. Ornamentation in the central area is variable in size and arrangement (note that areolae are absent from the central area). Striae are uniformly-spaced at the valve margin
Symmetrical biraphid - Valves are large and linear-lanceolate. Apices are cuneate. Striae are radiate. The central area includes a distinct stigma and scattered puncta. Areolae are coarse and easily visible in LM, measuring 18-20 in 10 µm.
Symmetrical biraphid - Valves are large, with cuneate apices. Striae are radiate, with a higher stria density near the apices. The central area is incomplete and characterized by irregular, scattered puncta. Areolae are coarse and easily visible in LM.
Symmetrical biraphid - Valves with protracted apices. A single, distinct stigma is present, placed relatively close to the valve margin. Short, marginal striae, or isolated areolae, at the central area.