This locally occurring species looks very similar to and could represent the Sparse Dove Snail, Costoanachis sparsa (Reeve, 1859). Shells from Southwest Florida differ ever so slightly from other varietals of this latter species, though, by details of the sculpture, including the deeply etched spiral lines below the suture (area separating two consecutive whorls). You’ll find that we cite the species in the Museum’s identification guide as “Costoanachis aff. sparsa”. The abbreviation “aff.” stands for the Latin affinis, a word that can be translated as "comparable to" or “related to.” Use of this abbreviation conveys the idea that the species is very similar to the Sparse Dove Snail, but could represent a separate entity. The snail in the image was collected from stranded seaweed on Sanibel by Rebecca Mensch in early 2015. Measuring in at about 8mm (0.32 inch), the two views of the snail were taken by yours truly under a Leica microscope. The snail's mantle and foot are whitish with brownish-gray blotches. The tentacles and siphon are of same colors, but the blotches become rings around those body parts. Read more about local mollusks on our Southwest Florida Shell Guide.