The Netted Pyram, Peristichia agria Dall, 1889 is a local gastropod of the hyper-diverse family Pyramidellidae. Its shell may reach 7 mm (about 0.3 inch), and the surface sculpture includes three spiral (“coiling”) cords (four on last whorl) crossed by about 20 axial ("vertical") ribs. The combination of spiral cords and axial ribs impart a reticulated, or net-like, pattern to the shell surface, and small nodules form at the intersections of the cords and ribs. The shell color is cream-white. Pyrams are parasitic snails, living on or in the bodies of other mollusks, worms, sea anemones, and crustaceans.
The Netted Pyram, Peristichia agria, from Sanibel. Photos by José H. Leal.