Keen’s Hairy Triton Shell, Monoplex keenae

Keen’s Hairy Triton Shell, Monoplex keenae. Shell collected off the beach at Punta Chivato, Baja California Sur, March 2022. Size: 13.4 cm (5.3 inches) x 7.6 cm (3.0 inches) x 6.2 cm (2.4 inches). Collection, photographs and identification courtesy of Colin Campbell, DVM, Punta Chivato, Baja California Sur.

Keen’s Hairy Triton Shell, Monoplex keenae. Shell collected off the beach in the greater Bahía de los Ángeles area, Baja California, May 1992. Size: 13.8 cm (5.4 inches) x 7.9 cm (3.1 inches). Collection, photograph and identification courtesy of Bob Hillis, Ivins, Utah.

Keen’s Hairy Triton, Monoplex keenae (Beu, 1970), is a gastropod mollusk that is a member of the Cymatiidae Family of Tritons. The shell is thick and heavy with a spindle-shaped outline, the exteriors are marked with thick spiral ridges and strong varices, and they have large apertures which have a thick outer lip that contains wide, double-teeth, and an interior lip that is narrow with ridges. The exterior of the shell is cream to light brown in color, with darker brown axial lines and light brown, dark brown or white sections on the varices that cover the body whorl and both the inner and outer lips of the aperture are dark brown and white in color; the siphonal canal and interior of the shell is white; the “hairy” periostracum is yellowish brown. Keen’s Hairy Triton shells reach a maximum of 15.5 cm (6.1 inches) in length and 8.9 cm (3.5 inches) in height.

Keen’s Hairy Triton reside on and within sand substrate, and are often found between rocks from the intertidal zone to depths up to 40 m (130 feet). They are found from Magdalena Bay, Baja California Sur to Northern Chile; in the Sea of Cortez they are found south of Mulegé, Baja California Sur. Keen’s Hairy Triton is very similar to and is often confused with the Giant or Neapolitan Hairy Triton, Monoplex parthenopeum, which has a global distribution but is not found in the Eastern Pacific Ocean.

Synonyms are Cymatium parthenopeum keenae, Monoplex parthenopium keenae, and Septa parthenopeum keenae.