Surirella Angusta Guide
Credit: Marina Potapova
  1. Keel low, alar wings absent
  2. Valves isopolar
  3. Striae 23-28 in 10 µm
  4. Each 3rd or 4th costae raised
  5. Valve face flat

The keel is low, no alar wings are visible. Valves are isopolar with a flat valve face. Striae are dense, 23-24 in 10 µm. costae number 7-8 in 10 µm, each third or fourth costa is raised. Valves are 15.5-60 µm long by 6.5-12 µm wide.