Surirella Stalagma Guide
Credit: Jonathan English, Marina Potapova
  1. Valves small
  2. Valves heteropolar
  3. Costae not visible in LM
  4. Fibulae short, wide
  5. Low keel, wider than the mantle

Valves are small and heteropolar, 11-16 µm long by 5-7 µm wide. The foot-pole is capitate, while the head-pole is rounded. The costae are numerous, 55 in 10 µm, so they are only visible in SEM. The fibulae are short and wide, with a density of 8-10 in 10 µm. The keel is low, and broad compared the the mantle.