Heteropolar

A valve with poles, or apices, of the apical axis having different shapes. Heteropolar valves are asymmetrical to the transapical axis. Example genera include Gomphoneis and Gomphonema.

Heteropolar
Image Credit: Pat Kociolek
The diatom Gomphoneis olivaceum is heteropolar and the headpole and footpole are distinguished from one another.