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Guide to Stephanodiscus yellowstonensis

E.C.Ther. and Stoermer 1984

Stephanodiscus Yellowstonensis Guide
Credit: Sarah Spaulding
  1. Valves concentrically undulate
  2. Areolae round
  3. Areolae 12-18 in 10 µm
  4. Marginal spines every 2-5 costae

Valves are concentrically undulate; only the valve margin or the valve center is in focus at one time. The areolae are round and arranged in fascicles of radial striae, separated by costae. Areolae are 12-18 in 10 µm. Striae are uniseriate in the center valve and multiseriate (2-5) near the margin. Marginal spines are present, positioned every 2-5 costae. Marginal fultoportulae are present, positioned below the spines. Central fultoportulae are also present in the valve center, singly or in a ring. One or more rimoportulae are present near a marginal spine, with a spine-like external extension.