Surirella Brebissonii Guide
Credit: Jonathan English, Marina Potapova
  1. Keel low, alar wings absent
  2. Valves large, heteropolar
  3. Valves with large size range
  4. Fibula density 5-6 in 10 µm
  5. Costa density 18-23 in 10 µm

Valves with large size range, 15.5-56.0 µm in length and 10-25 µm in width. Smaller valves are almost circular, but larger valves have one broadly rounded apex and one cuneately rounded apex. Costa density is 18-23 in 10 µm and fibula density is 5-6 in 10 µm.