Rhoicosphenia Abbreviata Guide
Credit: Marina Potapova
  1. Valves club-shaped
  2. Pseudoseptae present
  3. Raphe valve with full raphe system
  4. Rudimentary raphe valve with short raphe slits
  5. Central area oval

Valves are clavate, or club-shaped with rounded ends. In girdle view, frustules are distinctly arched. In valve view, the arch prevents resolution of the entire valve face at one level of focus. Pseudoseptum present at each pole. One valve possesses a fully developed raphe system, the other valve possesses short raphe slits.