Shell rather small for genus, about 35 mm in length (occasionally up to 46 mm), fusiform, consisting of 8 or 9 convex whorls, body whorl slightly ventricose. Suture distinct, wavy. Axial growth lines fine and inconspicuous.
Colour pale to reddish-brown, occasionally dark brown, with dark reddish-brown spiral cords and threads. Interspaces between axial ribs usually darker. Occasionally with a whitish band below periphery on later whorls.
Protoconch with 1-1,25 white, bulbous, glossy whorls, final ¼ whorl with 2-4 fine axial riblets, transition to teleoconch marked by a varix. Diameter 0.9-1.0 mm.
Teleoconch beginning with 3 primary spiral cords. Starting with second whorl, a fourth spiral cord appears adapically, on fifth or sixth whorl a fifth cord appears in lower suture. Fine, often reddish coloured, inconspicuous intercalated spiral threads appear from third teleoconch whorl on; their number increasing to 5-7 on body whorl, central one stronger.
Axial ribs equal, usually strong, interspaces as broad as ribs, often darker coloured. About 10 or 11 axial ribs on upper whorls. 10-12 on penultimate and 14 or 15 on body whorl.
Aperture ovate, white, pointed on upper end. aperture with siphonal canal about ½ of whole shell length. Columella smooth. Outer lip thin when juvenile, thickened in adult specimens. Inside with numerous strong lirae. Fully mature specimens often with 1-2 strong columellar fold(s). acquired in adult stage.
Siphonal canal shorter than aperture length, almost straight. Outer side sculptured with fine red spiral cords.
Operculum typical of genus, light brown.
Radula typical of genus, central tooth tricuspid, relatively large, base convex, both sides slightly convex, cusps rather strong and long, projecting below base. Lateral teeth relatively broad, curved, with 5 or 6 incurved, short, pointed cusps; outermost and innermost strongest, at inner end with a small denticle.

Axial ribs strong, 17-18 on last whorl, with microscopic axial growth-lines in the interspaces. Spiral ridges narrow, widely spaced, 4-5 on penultimate whorl, forming transverse nodules at the intersections with axial ribs, interspaces with 5-7 spiral threads, central thread strongest. Columella callus narrow, smooth. Outer lip ridged within. Reddish-brown with dark brown axial interspaces, spiral ridges light brown. 40 mm.
Distribution and habitat: Agulhas Bank, in 100-200 m (typical form).
Note: Granulifusus rubrolineatus appears to be a variable species. Narrow, yellowish specimens with weaker axial ribs and distinct continuous reddish-brown spiral ridges occur from East London to Natal, but apparently also on the Agulhas Bank where intermediate forms have occasionally been observed. Natal specimens are often found attached to Xenophora pallidula in 300-400 m and are difficult to distinguish from Granulifusus rufinodis (von Martens, 1901) from the west coast of Sumatra and Granulifusus poppei Delsaerdt, 1995 from the East African coast. DNA studies might shed some light on the relations between these species. Uncommon.

The likelihood that G. poppei may be a geographical variant of G. rubrolineatus is very unlikely as Agulhas Bank fauna does not extend into the tropical waters of northern KZN and East Africa. Agulhas Bank fauna has a very high degree of endemicity. A closely allied species is Granulifusus rufinodis (von Martens, 1901), described from off Sumatra. Granulifus poppei is a variable species from the east African coast reaching the Wild Coast in the Eastern Cape. G.
rubrolineatus is endemic to the Agulhas Bank off the southern Cape Province (Type locality Agulhas Bank). Off the SW Cape, in much deeper waters, occurs the rare G. faurei (Barnard, 1959), a cream coloured species with weaker sculpture. In the past, G. rubrolineatus has been misidentified as G. faurei and G. poppei was misidentified as G. rubrolineatus probably due to the striking red spiral lines present in that species

G rubrolineatus is a remarkably variable species: Most specimens from Agulhas Bank and Algoa Bay are dark brown in colour, with lighter coloured strong axial ribs, occasionally with a short, broad spire. The holotype from Agulhas Bank is almost identical to this brown form, but lighter coloured. We occasionally observed yellowish or pale brown specimens with weak axial ribs and distinct reddish-brown spiral cords also from Agulhas Bank and off East London. Specimens from the East African coast (Madagascar, Comoro Islands, Zanzibar and southern Somalia) belong to this yellowish form with distinct reddish-brown spiral cords. These two forms can be linked together, intermediate forms can occasionally be observed.
The brown coloured form is easy to recognize, but the yellowish form with reddish-brown spiral cords should be compared with the following species:
G. rufinodis differs by having a larger adult size, a somewhat longer spire and longer siphonal canal, stronger axial ribs, and stronger primary spiral cords. G poppei differs by its slender spire, the shorter and broader siphonal canal, the narrowly elongate aperture, the more constricted suture, and the rather strong axial ribs. G. consimilis differs by its more elongate spire, the longer siphonal canal, the more constricted suture, the subsutural concavity, and the stronger spiral and axial sculpture.
For differences with G benjamini we refer to the remarks under that species.

Range and habitat: From South Africa. Agulhas Bank northwards to southern Somalia. Collected 100-638 m deep.