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Guide to Stephanodiscus oregonicus

(Ehrenb.) Håk. 1986

Stephanodiscus Oregonicus Guide
Credit: Loren Bahls
  1. Valves small
  2. Concentric undulation distinct
  3. Fascicles multiseriate at valve margin
  4. Central areolae disorganized or weakly radiate
  5. Marginal spine on every interfascicle

Valves are small, at less than 40 µm in diameter. Fascicles are multiseriate at the valve margin, where they are always composed of 3 or more rows of areolae. The valve face has strong concentric undulation, with either a convex or concave central area. The areolae in the central area are disorganized or arranged in weakly radiate rows. A marginal spine is present on every interfascicle.