Stauroneis siberica has lanceolate to elliptic-lanceolate valves with rostrate to subcapitate apices. The striae are very fine and number 24-32 in 10 µm. The stauros is typically narrower toward the valve margins and may, or may not, contain short striae. Areolae bordering the stauros are more prominent and more widely spaced than areolae elsewhere.