Aulacoseira Humilis Guide
Credit: Jonathan English, Marina Potapova
  1. Small valve size
  2. Valve face concave or convex
  3. Long, thin spines at the end of each costa
  4. Extremely fine areolae in double rows
  5. Valve face with large areolae

Valves are 5-9 µm in diameter and have a mantle height of 2-5 µm. The valve face is strongly convex or concave and covered with large areolae. The striae are straight, composed of two rows of fine areolae, terminate in a single large areola, and are situated between raised costae. There is a long, thin spine at the end of each costa.