Many believe that the Lightning Whelk, Sinistrofulgur sinistrum, is the only left-handed gastropod in our area. The fact is there is a handful of local species in the family Triphoridae that also display that feature. (Most species of Triphoridae are left-handed.) Of those, the most commonly found is the Modest Triphora, Marshallora modesta (CB Adams, 1850). The shell is small reaching at most 5mm (about 0.2 inch), and typically with three spiral rows of whitish beads set against a glossy-brown background. Triphorids live in association with sea sponges (which in turn may be found living on rocks and other hard surfaces).
The Modest Triphora, Marshallora modesta, from Sanibel. Photo by José H. Leal.