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Guide to Achnanthidium atomus

(Hust.) Monnier, Lange-Bert. and Ector 2004

A Atomus Guide
Credit: Marina Potapova
  1. Raphe valve with strongly radiate striae
  2. Rapheless valve with more widely spaced, parallel striae
  3. Valves elliptical to linear-elliptical
  4. Areolae small, not visible in LM

Valves are elliptical to linear-elliptical. The raphe valve is concave and the rapheless valve is convex. Terminal raphe fissures are absent. Striae are strongly radiate on the raphe valve and parallel on the rapheless valve. The raphe valve has a transverse fascia, while the rapheless valve lacks a central area. The axial area on both valves is narrow and linear.