Reaches 0.19-0.59 in (5-15 mm) in diameter. Carapace is conical, with six gray or white fused calcareous plates forming a lateral wall. The dorsal anterior plate is the largest. The carine is posterior and two pairs of plates are located laterally. On top, two pairs of short calcareous and articulated plates, the terga and scuta (one pair on each side) form the operculum in a diamond-shaped arrangement; it encloses the mantle cavity and can be opened and closed by muscles. When rotated laterally, they form an aperture through which leads to the mantle cavity and the six pairs of birramous cirri bordered by chaetae, the first three being shorter than other three. Tissue inside opercular aperture is usually white or pinkish. Attaches to rock using the flattened and broad membranous attachment disc.
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