Peronia Fibula Guide
Credit: Rob Kimmich, Ian Bishop
  1. Sternum narrow
  2. Valves heteropolar
  3. Marginal spines present

Frustules are heterovalvar, one valve with a raphe and the other with a rudimentary raphe, or no raphe. A narrow central sternum is present. Valves are heteropolar, with a narrow, rounded footpole and a wider headpole, which is variable in shape. Marginal spines are present.