Shell with five or six rounded whorls. Sutures slightly indented. Sculpture of incised spiral lines on entire shell. Well-defined parietal shield tinged with mauve. Color grayish-white, gray, or bluish-gray with irregular brown markings. Earlier whorls usually dark-brown, aperture yellow within. This species prefers to settle on dead tree trunks or dead wood structures. The two photos of the unusually bluish-shelled snails living on dead black mangrove trunks were taken by Dr. José H. Leal on Cayo Costa State Park on October 25, 2014.

Shell size to 25 mm; shell with six or seven rounded whorls. Sutures slightly indented. Spiral grooves on last few whorls. Color gray to reddish to brown with irregular darker markings. Unlike its close relative, the cloudy periwinkle, which forms aggregations on dead tree trunks and other dead wood, the mangrove periwinkle prefers to live on live mangrove trees, in particular on the prop roots, trunk, and branches of red mangrove trees, as seen in the supplementary photo. Mangrove periwinkles browse on the film of fungi and algae that grows on the mangrove bark. Individuals in this species spend all their lives out of water, except for the first couple of months of their larval life. The first supplementary photo was taken by Amy Tripp on Kice Island, Collier County, November 2014. The second supplementary photo includes three Mangrove Periwinkles from the from the bay side of Sanibel.

Shell size to 15 mm; shell pointed, solid, whorls with flat sides. Sculpture consisting of widely spaced spiral grooves. Aperture length about half of shell length. Color white with dark-brown, wavy or zigzag lines, and broad band of purplish-brown color on median part of last whorl; this band also visible in abapical part of previous whorls. Found on splash zone (supralittoral), on rocks or other hard substrates. Species previously listed as Nodilttorina interrupta (Philippi, 1847). The supplementary photo was taken by Diane Dringoli Thomas in October 2019 on the bay side of Sanibel.