Gomphonema Amerhombicum Guide
Credit: Ian Bishop
  1. Valves clavate
  2. Striae biseriate
  3. Axial area rhombic
  4. Striae convergent at headpole
  5. Pores in rows of 1-2 on girdle band

Valves are clavate, with rounded poles. The axial area is large, mostly rhombic, but expands mid-valve where it is more circular. Striae are biseriate. Striae are weakly radiate, becoming parallel to convergent at the headpole and increasingly radiate at the footpole. In girdle view, frustules are rectangular to trapezoidal and 1-2 rows of pores are present on the girdle bands,