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 - 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.
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 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 diameter.
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 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.