Semiorbis Rotundus Guide
Credit: David Burge
  1. Valves semi-circular
  2. Dorsal wing-like projections present
  3. Apices subrostrate

Valves are strongly arched and semicircular. Apices are subrostrate and may be recurved. Transapical striae are separated by externally thickened transapical costae, which at the dorsal margin, form wing-like projections.