Hannaea Guide
Credit: Becky Bixby, Megan Otu
  1. Valves arched
  2. Poles capitate to rostrate
  3. Valve with central ventral swelling
  4. Faint (ghost) striae near central swelling

Valves are linear and arched. One or two rimoportulae occur on each valve, located near the valve ends. The ventral (concave) side of the valve has a central swelling. Faint, or ghost striae, are often present near the center of the valve.

Hannaea is characteristic of oligotrophic streams and large lakes, where it grows attached in tufted colonies to benthic surfaces.