Surirella Suecica Guide
Credit: Jonathan English, Marina Potapova
  1. Keel low, alar wings absent
  2. Valves 14-34 µm long, 7-9.5 wide
  3. Costa density high
  4. Valves narrow, clavate
  5. Fibulae short

Valves are heteropolar, narrow and clavate, with size ranges of 14-34 µm long and 7-9.5 µm wide. The density of costae is high (30-36 in 10 µm), so costae may not be visible in LM. Fibulae are short, and number 9-12 in 10 µm.