Last week, we examined the Elegant Dosinia, Dosinia concentrica. Today I want to introduce its closest relative, Dosinia discus (Reeve, 1850). The two species have shells that are very similar in size (about 2.75–3 inches), in their circular shape, and white color, but the Disk Dosinia differs from its “sister species,” above all, by having twice as many commarginal (“concentric”) ridges, about 16–20 per centimeter (40–48 per inch).
