5; Hustedt, 1930, p. 789, Fig. 461; Cupp, 1943, p. 150, Fig. 108; Hendey, 1964, p. Ill, Plate 6, Fig. 6; Hasle, 1975, Figs. 149-151;Takano, 1979; von Stosch, 1980; von Stosch, 1987, p. 42, Figs. 46-59; Takano, 1990, pp. 298-299.
Cells solitary or in ribbons.
Cells in girdle view rectangular to square.
Cells in valve view triangular, rarely biangular or quadrangular.
Marginal ridge membraneous.
Each valve with a central bilabiate process with long external tube.
Valve face with radial rows of poroid areolae starting from a nonperforated area around the process. Conspicuous elevations at valve corners.
Proximal to each elevation a depression in valve face across the corners. Chloroplasts, numerous small bodies.
Characters showing differences between species: Solitary or in ribbons.
Direction of marginal ridge in relation to valve mantle.
Structure of marginal ridge.
Shape of valve mantle.
Height of elevations.
Size of valve areolae.
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