Brachysira serians

Valves are lanceolate with narrowly rounded apices. The striae are slightly radiate to parallel throughout the valve. At the apices, the striae are composed of a single areola. The axial area is linear and distinct; the central area is asymmetrically rounded. The raphe is positioned between two external, longitudinal ribs. The raphe is straight with straight proximal fissures and T-shaped distal fissures. Areolae are elongated rectangular slits with rounded ends, oriented to the transapical axis. Spaces between the areolae give the appearance of longitudinal undulations. Thick, external ribs are present at the valve margins. The mantle possesses a single row of elongated areolae. One or two Voigt faults are present on the secondary side of the axial area.

In SEM, the internal distal raphe fissures terminate at small helictoglossae. The areolae are covered internally with flat hymenes. Externally, a series of siliceous ridges may extend longitudinally on the valve face.

The first description of B. serians appeared in Kützing (1844), with a valve length of 94 µm. Kützing's illustration (Taf. 30, fig. 23) presents the species in valve and girdle views.

The images presented here are not consistent with the type of Kützing (Van de Vijver et al. 2022). This page may be updated in the future.