Triangular Rock Shell, Acanthais triangularis

Triangular Rock Shell, Acanthais triangularis. Size: 2.2 cm (0.9 inches) x 2.0 cm (0.8 inches). Shell courtesy of the commercial fishermen of the greater Los Cabos area, Baja California Sur, May 2013.

The Triangular Rock, Acanthais triangularis (Blainville, 1832), is a gastropod mollusk that is a member of the Muricidae Family of Rocks. The shell consists of four to five whorls with a series of knobs begin at the shoulder and spiral along the body whorl of which two equal sized knobs project as blunt spines at the outer lip of the wide aperture and a low blunt spire. The exterior of the shell is white, with most displaying some rust to light brown blotches; the interior is smooth and white. Triangular Rock Shells reach a maximum of 3.0 cm (1.2 inches) in length and 2.7 cm (1.1 inches) in height.

Triangular Rock Shells are found attached to rocks in the intertidal zone to depths up to 5 m (15 feet). They are found in the greater Los Cabos area, Baja California Sur to Peru, including the Galapagos Islands. They are found throughout the Sea of Cortez.

Synonyms include Purpura carolensis and Thais triangularis.