SHELL. Low-spired, of medium size (up to 80 mm in length) with seven shouldered teleoconch whorls.
Protoconch of about two and one-half conical volutions, ending in small crescentic varix.
Spiral ornamentation on first teleoconch whorl of three rounded cords; on second and third whorls, one additional cord added to each primary spiral cord until body whorl and siphonal canal covered with numerous spiral cords all of approximately same size.
Axial ornamentation on first two teleoconch whorls of nine ribs, varying from rounded to sharply angulate; angulate ribs with small open spines at shoulder. On third whorl, every third rib strengthened to form varix with short, sharp closed spine at shoulder; intervening ribs forming rounded intervarical ridges lacking spines. Body whorl with two weak intervarical ridges, nodulose at shoulder, periphery and base of whorl, nodules decreasing in strength anteriorly. Three heavy, rounded varices per whorl, each with three apically curved spines, spine at shoulder much elongated in some specimens. Siphonal canal with one spine near base of body whorl. Suture simple, slightly impressed.
Aperture rounded; outer lip formed by flange in advance of varix, margin crenulated and notched by median grooves in major spines. Notches at periphery and base of body whorl wider and deeper than others and delineating large labral tooth; margin of outer lip somewhat outwardly recurved anteriorto this tooth, forming strombid-like notch. Anal notch small. Anterior portion of inner lip appressed; posterior two-thirds free-standing, narrow, smooth.
Siphonal canal moderately long to long; straight; previous canals fused into tube, open by narrow slit; spinose only immediately adjacent to base of body whorl.
Colour ivory to golden brown, with three diffuse brown bands; one each at shoulder, periphery and base of body whorl; these bands best seen on inside of shell. Spiral cords brown, especially adaperturally from axial ridges; aperture white; deep inside aperture often light brown, with aforementioned darker bands. Operculum reddish brown; subterminal nucleus, surrounded by numerous faint concentric ridges.
This subspecies differs from other subspecies of M. brevispina in the shell having a multispiral protoconch and is almost certainly the most primitive form of this species. It is for this reason that a detailed description has been offered. The teleoconch differs from the typical form of M. brevispina in having a less inflated body whorl, a higher spire, and a smaller aperture lacking the large flaring inductura. The spiral cords are heavier, the varical spines are always developed, and the siphonal canal is longer in proportion. The shell of some juvenile specimens of the typical subspecies are, however, very similar to M. brevispina macgillivrayi. The presence of the brown colour bands on the shell is also distinctive; this is one of only two species of Murex to have them, although there is an indication of banding in M. brevispina ornamentalis.