Stria density is based on the number of striae in an arc of circumference. The density = circumference * 10 / total number of striae on the valve. In Figure 1, the stria density is equal to (54.3 µm) (10) / 21, or 3.9 striae in 10 µm of circumference.
Stria count is based on the number of striae in a chord of the valve face. In Figure 2, the chord crosses 5 striae, giving a count of 5 in 10 µm.
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