Sculptured Keyhole Limpet Shell, Diodora inaequalis

Sculptured Keyhole Limpet Shell, Diodora inaequalis. Shell collected off the beach in the greater Cabo San Lucas area, Baja California Sur, November 2020. Size: 2.4 cm (1.0 inch) x 1.6 cm (0.6 inches).

The Sculptured Keyhole Limpet, Diodora inaequalis (G.B. Sowerby I, 1835), that is gastropod mollusk that is a member of the Fissurellidae Family of Keyhole Limpets. They are also known as the Rocking Keyhole Limpet and in Mexico as lapa de agujero tallado. The shell is elongated, with a base that is slightly narrower at the anterior end than at the posterior end, nearly parallel sides that are arched, such that the shell will rock on its ends if placed on a flat surface and an apex that is set forward. The orifice is elongated, and, in smaller individuals, notched on both sides, and the exterior of the shell is sculpted with fine radiating lines and even finer concentric lines. The exterior of the shell is gray with brown rays; the interior is white with a gray callus border. The Sculptured Keyhole Limpet Shells reach a maximum of 2.7 cm (1.1 inches) in length and 1.6 cm (0.6 inches) in height.

Sculptured Keyhole Limpets are found under rocks during the daylight hours. They emerge and feed during the night by scraping algae from the rocks by use of their radula. They are found in the intertidal zone to depths up to 37 m (120 feet). They are known throughout the Sea of Cortez and south to Ecuador. They have not been documented from the West Coast of Baja.