The Smooth Risso, Zebina browniana (d'Orbigny, 1842), is one the many micromollusks found on Sanibel and Captiva, but the only one from the gastropod family Zebinidae found locally. Reaching not more than 0.2 inch in size, it qualifies as a true micromollusk, as, by definition, micromollusks are those having shells not larger than 5 mm, or about 0.2 inch. The shell shape is conical and, as the common, or vernacular, name implies, smooth and devoid of any sculpture, smooth. The shell is also translucent, sometimes transparent, in particular when the snail is alive.
The Smooth Risso, Zebina browniana from Sanibel. Photo by José H. Leal.