Guide to Stephanodiscus oregonicus
Credit: Loren Bahls
- Valves small
- Concentric undulation distinct
- Fascicles multiseriate at valve margin
- Central areolae disorganized or weakly radiate
- 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.