Just like the Netted Pyram, Peristichia agria Dall, 1889, presented last week in this column, the Tower Pyram, Peristichia toreta Dall, 1889, is a local gastropod of the hyper-diverse family Pyramidellidae. The Tower Pyram shell is slender, elongate, reaching 11 mm (about 0.4 inch) in length. The shell sculpture includes three spiral cords and single smooth, narrow spiral thread just above suture (the groove between two whorls); about 30 narrow axial ribs are present. As with the Netted Pyram, a reticulated pattern results from the intersections of spiral cords and axial ribs. The shell color is pure white. This species is more slender, has a relatively smaller aperture, and more delicate and regular sculpture than the Netted Pyram. Pyrams are parasitic snails, living on or in the bodies of other mollusks, worms, sea anemones, and crustaceans.
The Tower Pyram, Peristichia toreta, from Sanibel. Photos by José H. Leal.