Guide to Asterionella ralfsii var. americana
- Valves heteropolar
- Headpole ending truncate
- Footpole rounded, rostrate
- Rimoportula present at headpole
- Spines present
Valves heteropolar and very narrow. Headpole capitate ending truncate, foot pole rostrate ending rounded and more narrow than the valve center. Rimoportulae visible at the headpole. Spines present along the valve margin.