Black Murex Shell, Muricanthus nigritus

Black Murex Shell, Muricanthus nigritus. Size: 6.6 cm (2.6 inches) x 4.6 cm (1.8 inches). Shell collected within the intercoastal waterway, Puerto Adolfo Lopez Mateos, Baja California Sur, April 2017.

The Black Murex, Muricanthus nigritus (Phillipi, 1845), is a gastropod mollusk that is a member of the Muricidae Family of Rock Shells that is also known as the Northern Radix  or the Black and White Murex.  In Mexico they are called  busano negro or caracol burro negro. They are solid, fairly globose shells which have six whorls, a low to moderate pointed spire, and a long mostly enclosed siphon canal. They have raised and marked varices with short, pointed, open spines. The Black Murex can be confused with the Ambiguous Murex Shell, Muricanthus ambiguus (longer, less pointed and more frilled spines). The exterior of the shell is white with black stripes and varices, with the amount of black coloration varying between specimens. The interior is porcelaneous white. Black Murexes reach a maximum of  20.0 cm (7.8 inches) in length and 14.0 cm (5.5 inches) in height.

The Black Murex is found on rock, gravel, and sand bottoms, in the intertidal zone to depths up to 61 m (200 feet). Their primary prey are barnacles and bivalves; in turn they are preyed upon by crabs, fish, and sea stars. They range from Magdalena Bay to Cabo San Lucas, Baja California Sur and are found throughout the Sea of Cortez.

Synonyms include Murex negritus and Muricanthus negritus.