Cyclostephanos Dubius Guide
Credit: Lena Ivarsson
  1. Valve concentrically undulate
  2. Marginal costae distinct
  3. Alveoli distinct
  4. Central areolae organized or scattered

Valves are strongly concentrically undulate. Marginal costae alternate with marginal chambers, called alveoli. The central areolae of large specimens are often organized into striae, while the central areolae of smaller specimens are more irregular and scattered. Spines are absent.