The shells of Petaloconchus nigricans (Dall, 1884) are long, narrow, brown tubes sculpted with longitudinal ridges. As with other members of the family Vermetidae, the Dark Worm Snails live in agglomerations that form massive structures. The largest such cluster from Sanibel in the National Shell Museum Collection was found in September 2016 by Michael Reardon. That cluster (photo) measures 23 cm (about 9 inches), and the largest shell aperture diameter in this cluster measures about 3 mm (about 0.12 inch). Dr. Rüdiger Bieler from the Field Museum of Natural History identified the cluster in the photo. Read more about the Dark Worm Snail and other local mollusks in the Southwest Florida Shells Guide.
