Unwashed Ark Shell, Fugleria illota

Unwashed Ark Shell, Fugleria illota. Size: 2.5 cm (1.0 inch) x 1.8 cm (0.7 inches). Shell collected off the beach at Km 26, Cero Colorado, Baja California Sur, March 2010. Identification courtesy of Bob Hillis, Ivins, Utah.

The Unwashed Ark, Fugleria illota (G.B. Sowerby I, 1833), is a bivalve mollusk that is a member of the Arcidae Family of Arks. They are also known as a Dirty Ark. The shell has an oval profile, with a well-rounded beak. The shell is thin in substance and inflated. The exterior is sculpted with numerous, rounded radial ribs. The ribs are thicker at the posterior end. The shell is dirty white to gray and covered with a brown hair-like periostracum. The Unwashed Ark reach a maximum of 24.9 cm (9.8 inches) in length and 17.9 cm (7.1 inches) in height.

Unwashed Arks are found attached to rocks, in the intertidal zone to depths of 73 m (240 feet). They range from San Ignacio Lagoon, Baja California, to Peru, including the Galapagos Islands. They are found throughout the Sea of Cortez with the exception of the extreme northern portions.

Synonyms include Arca tabogensis, Byssoarca illota, and Barbatia illota and Byssoarca illota.