Eye-of-Judas Shell, Tribulus planospira

Eye-of-Judas Shell, Tribulus planospira. Size: 5.0 cm (2.0 inches) x 4.5 cm (1.8 inches). Shell collected off the beach in the greater Los Cabos area, Baja California Sur, August 2011.

The Eye-of-Judas, Tribulus planospira (Lamarck, 1822), is a gastropod mollusk that is a member of the Muricidae Family of Rocks. The shells are bowl shaped that consist of three whorls, that make up the majority of the shell, an almost flat spire and a very large aperture. The exterior shell surface is sculpted with low and high ribs, that follow along the whorls and are most visible at the shoulder and at the outer lip of the aperture. The exterior of the shell is tan to brown; the interior is white with reddish brown ribs running from the inside and outside lips and the inside lip also has a black rib that runs at an angle. The Eye-of-Judas Shells reach a maximum of 8.3 cm (3.3 inches) in length and 7.5 cm (2.9 inches) in height.

Eye-of-Judas Shells are found on attached rocks, in the intertidal zone to depths up to 5 m (15 feet). They have a limited distribution along the coast of Baja being found only in the greater Cabo San Lucas area, Baja California Sur. They range as far South as Peru and are also found in the Galapagos and Revillagigedo Islands.

Synonyms include: Haustrum pictum, Purpura lineatum, Purpura planospira, and Thais planospira.