Nitzschia Exilis Guide2
  1. Valves delicate, narrowly lanceolate
  2. Breadth 2-3 µm
  3. Fibulae 15-17 in 10 µm

Valves are delicate, narrowly lanceolate with apices rostrate and subcapitate. Keel strongly excentric. Striae are not resolvable in the light microscope.