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Guide to Gyrosigma attenuatum

(Kütz.) Rabenh. 1853

Gyrosigma Attenuatum Guide
Credit: Joanna Gauthier
  1. Valves slender, sigmoid
  2. Central area longitudinally elliptical
  3. Longitudinal striae more coarse than transverse striae

Valves are slender, sigmoid and up to 255 µm in length. The central area is elliptic, and elongate. The longitudinal striae are coarser than the transverse striae, so that the longitudinal striae are more distinct than the transverse striae. For most of the length of the valve, the raphe is straight. Near the apices, the raphe is clearly sigmoid.