Guide to Aulacoseira herzogii

Valves are 3-7 µm in diameter and have a mantle height between 7-14 µm. The ratio of mantle height to valve diameter is either equal to, or greater than, 1. The straight rows of mantle areolae are often not resolvable in the light microscope and number 30-32 per 10 µm. These small areolae, if visible in LM, appear circular, 27-37 per 10 µm along the pervalvar row. On the valve mantle, two diametrically opposed grooves containing no areolae extend the entire length of the valve and two large, pointed separation spines diametrically opposed on the valve face extend in the plane of the mantle onto grooves of the neighboring valves. The planes of the large spines and the grooves are at right angles to each other. Smaller, broadly pointed spines are present at the end of each costa. Valves lack linking spines. The ringleiste is solid and relatively shallow.