Nitzschia Sigmoidea Guide
Credit: Stephanie Robson
  1. Valves large
  2. Valves sigmoid
  3. Apices gently hooked
  4. Striae 24-26 in 10 µm
  5. Fibulae 4-6 in 10 µm in center valve

Valves are large and sigmoid. Apices are gently hooked. Striae are distinct and parallel throughout the valve and distinct. Fibulae are continuous through the central valve, but otherwise irregularly spaced.