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Guide to Aulacoseira granulata var. angustissima

(O.Müll.) Simonsen 1979

Aulacoseira Granulata Angustissma Guide
Credit: Jonathan English, Marina Potapova
  1. Mantle height to valve diameter ratio > 3.2
  2. Valve diameter 2.5-4 μm
  3. Separation valves with 1-2 long spines
  4. Rows of mantle areolae in separation valves straight, or slightly curved to right
  5. Rows of mantle areolae in linking valves curve to right

The ratio of the mantle height to valve diameter is greater than 3.2. The rows of mantle areolae are curved to the right (dextrorse), but often are almost straight and parallel to pervalvar axis in separation valves. Separation spines originate from two pervalvar costae. Most separation spines are 2-6 µm long and broadly triangular, but 1 or 2 spines per valve are very long, almost equal in length to the height of the valve mantle.