Shell of the Week: The Smooth Sundial
Psilaxis krebsii (Mörch, 1875) is a marine snail of the sundial family Architectonicidae that may reach about 14 mm (about 0.5 inch) in diameter. The characteristic “UFO-shaped” shell has slightly convex whorls; the shell surface is basically smooth, except for very weak spiral cords near the shell periphery (the “outer rim” of the shell) and a prominent cord at the periphery. The umbilicus is wide and deep, with the “staircase-like” edge that is typical of many sundial species. The background color is cream, and faint, reddish-brown flame-shaped markings may be present on the spire (the “upper” shell surface). The species has a very broad distribution from North Carolina to Florida and the Caribbean, Gulf of Mexico (in deeper water), Bermuda, and the Caribbean, south to northeastern Brazil. Illustration by James F. Kelly for the Museum’s Digital Imaging Project.