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Guide to Achnanthidium pyrenaicum

(Hust.) H.Kobayasi 1997

A Pyrenaicum Guide
Credit: Marina Potapova
  1. Terminal raphe ends curved to the same side of the valve
  2. Striae mostly parallel, may be slightly radiate in the valve center and slightly convergent at the ends
  3. Fascia usually present on raphe valve

Valves are linear-lanceolate with slightly drawn-out ends, often slightly asymmetrical about median transapical plane. The raphe valve is concave and rapheless valve is convex. The terminal raphe fissures are curved to the same side of the valve. Striae are parallel throughout both valves, or slightly radiate in the middle and slightly convergent at the ends. The striae are uniseriate with 2-4 areolae per stria. A fascia, or subfascia, is usually present on the raphe valve.