Compare Stauroneis subborealis

Larger specimens of S. subborealis may be distinguished from S. beeskovea by more widely spaced and less radiate striae, a smaller length to width ratio, and proximal raphe ends that are curved rather than straight. Stauroneis subborealis is smaller than S. subaustralis (46–142 µm long, compared to 85–165) and has a higher stria density (17–20 in 10 µm, rather than 16 in 10 µm) and areola density (18–22 in 10 µm, compared to 16–18 in 10 µm). Smaller, linear specimens of S. subborealis are similar in size and valve outline to S. subgracilis, but US populations of S. subborealis also include much larger specimens with a lanceolate shape. Stauroneis pergracilis has narrower and more distinctly protracted apices than S. subborealis. Stauroneis gracilis has elliptic-lanceolate valves, not linear or strictly lanceolate valves.