| Valve diameter (µm) | 6–15 | 7–11 | 10–28 |
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| Mantle height (µm) | 4–8 | 7–17 | 6–11 |
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| Discus | flat | flat | flat to slightly convex |
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| Areola density on discus (in 10 µm 2 ) | 98–108 | no areolae | not reported |
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| Valve face areolae | evenly distributed over entire valve face | only present on valve face periphery | irregularly scattered on valve face |
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| Velum | not observed | two bars, most often form a cross | not reported |
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| Orientation of pervalvar striae | parallel to pervalvar axis | parallel to pervalvar axis | parallel to pervalvar axis |
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| Number of pervalvar striae (in 10 µm) | 20–24 | 20–30 | 13–16 |
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| Number of areolae on pervalvar striae (in 10 µm) | 35–45 | 25–48 | 13–14 |
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| Spine shape | long, straight to slightly bent, distal ends pointed, blunt, club- or anchor- shaped | short, tapered, with anchor-shaped ends | short, spatulate, with anchor-shaped ends |
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| Spine frequency | on each to every third mantle costa | on every 2–3 (rarely 4) mantle striae | every few striae |
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| Length of spines (µm) | 1.1–2.0 | 0.7–1.5 | not reported |
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| Width of ringleiste | 10–15 % of valve diameter | slight swelling of the valve | 20 % of valve diameter |
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| Rimoportulae | one per valve near the inner ringleiste | not reported | not reported |
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