Black Murex, Hexaplex nigritus

Black Murex, Hexaplex nigritus. Size: 6.6 cm (2.6 inches) x 4.6 cm (1.8 inches).

The Black Murex, Hexaplex nigritus (Phillipi, 1845), is a member of the Muricidae Family of Rock Shells that is also known as the Northern Radix , Black and White Murex and the Northern Radix and in Mexico as busano negro and 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, Hexaplex ambiguus (long, 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. The Black Murex have a maximum length of 20.0 cm (7.8 inches).

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 the Cabo San Lucas, Baja California Sur and are found throughout the Sea of Cortez.

Synonyms include Murex negritus and Muricanthus negritus.