The shell is moderately small for the genus (maximum length 16 mm) and broadly fusiform. The spire is high, consisting of about two and one-fourth nuclear whorls and four weakly convex postnuclear whorls. The suture is weakly impressed. The body whorl is moderately large and rounded. The aperture is small and ovate, with a broad and very shallow anal sulcus. The outer apertural lip is erect and strongly undulate at its margin; the inner surface of the outer lip is strongly lirate. The columellar lip is detached and strongly erect. The siphonal canal is moderately long, narrowly open to the right, and distally recurved.
The body whorl bears five heavy, fimbriate varices, reflected away from the direction of growth, producing a concavity in the receding edge. Axial growth striae composed mainly of intritacalx may be seen between the varices. Spiral sculpture consists of seven cords on the body below the shoulder margin, three major and four minor intercalary cords, and a few almost obsolete cords on the shoulder. Between the body and the canal there is a marked gap in prominent sculpture, the area bearing only six low7 threads. The canal bears two major cords. All cords are scabrous, but on the leading edge of each varix they become densely imbricate; in this area the scales coalesce to form undulate lamellae.
Shell color is white, overlaid with a thick frosting of flat-white intritacalx. The aperture is porcelaneous white.
This species was originally described as Murex gravidus Hinds, 1844, a name preoccupied by M. gravidus Dujardin, 1837, a fossil species. The present replacement name is here introduced in honor of Dr. William K. Emerson, American Museum of Natural History.

Western coast of Africa: Cape Blanco, Mauritania, to Luanda Harbor, Angola.