Masked Cup-and-Saucer Shell, Crucibulum personatusun

Masked Cup-and-Saucer Shell, Crucibulum personatusun. Shell collected along the shore of Loreto, Baja California Sur, October 2019. Size: 3.5 cm (1.4 inches) x 2.9 cm (1.1 inches). Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.

The Masked Cup-and-Saucer Shell, Crucibulum personatusun (Keen, 1958), is a gastropod mollusk that is a member of the Calyptraeidae Family of Cup-and-Saucer and Slipper Limpets. They are known in Mexico as picacho. The shell has a wide, irregular, oval profile with the shape being determined by the contour of their attachment point. Their apex is moderately high with a recurved apex and they are marked by radial rays and concentric ridges. They may have fine nodes on the exterior and the margin of the shell is not serrated. The septum (internal cup) is flattened and not attached at the margin. The external color varies and may be brown, gray, reddish-brown or white. The interior of the cup is white, often with a dark center. The Masked Cup-and-Saucer Shells reach a maximum of 3.5 cm (1.4 inches) in diameter.

Masked Cup-and-Saucers are found attached to rocks and shells in the intertidal zone depths up to 50 m (165 feet). They are found throughout the Sea of Cortez and southward along the coast of the mainland to Guatemala. They have not been documented along the west coast of Baja.