Shell from 25 to 53 mm in height, thin but solid, shape fusiform with long siphonal canal. Spire angle 46°-55° (knobs included), 34°-41° when using the suture as measuring point. Colour while to dirty white, occasionally with brownish area between axial ribs, ornamented with 2-7 reddish-brown spirals on the penultimate, 8-12 on the body whorl. In some specimens the brownish areas join into a broad brownish band situated under the white axial ribs. One specimen without any coloured spiral, but brown axial pattern between the knobs only, is known from New Caledonia .
Protoconch smooth, globose, 1.2-1.6 mm in diameter, consisting of 1.25-1.50 whorls, the first whorl deviated from coiling axis by about 45°. Teleoconch consisting of about 6 whorls. First whorl with one primary spiral cord, on second or third whorl a second spiral cord appears between shoulder and suture, 2 or 3 on penultimate and 8-12 on body whorl. Primary spiral cords weak, in some specimens hardly visible and indicated by the presence of coloured spirals only. Some specimens with well visible primary spiral cords show 2 or 3 (rarely 5) intercalated secondary spiral threads between each pair of primary cords, the middlest usually broader, interspaces a narrow groove. On body whorl occasionally 5-13 fine cords above carina, of which 2 or 3 occasionally reddish-brown coloured. Up to 30 fine spiral cords on siphonal canal, 4-10 adapical ones well visible.
Spire whorls with 8 or 9 (rarely 7) broad axial ribs. Body whorl with 7-9 (8 or 9 in specimens with developed secondary spirals, 7 in specimens with smooth surface) broad and more or lesser developed axial ribs, running from just above shoulder down to about halfway base, forming a strong knob on carina. Aperture ovate, pinched at both ends, whitish. Outer lip with 17-20 internal lirae, adapical ones arranged 2 by 2. Lip mostly smooth, sometimes slightly furrowed. Columellar callus white to dirty white, thin, smooth, glossy. Siphonal canal straight, between whorls and middle occasionally with torsion, resulting in a siphonal lip curved back when seen laterally. Operculum light to dark brown, somewhat smaller as aperture, shape semi-oval, above rounded, lower side pointed, with terminal nucleus.

S. excelens differs from S. lineatus by the more axially orientated ribs (instead of broad short spines on carina), and by the presence of an additional spiral cord already present on the second or third teleoconch whorl. In S. lineatus the first whorls are more conical with a more developed keel on carina, usually closer to the lower suture. A smooth form (similar to the holotype) and a form with spiral sculpture (similar to paratype) co-exist with a number of intermediates, a phenomene also observed in S. lineatus. We cannot find evidence to split this new species in more than one taxon and conclude that these 2 forms fall within the variability of the species which is normal for the genus.
Separating S. excelens from S. lineatus with the naked eye is easy, based on the presence of the shape of the shoulder and the form of the spines or axial knobs. Under magnification however, the variability in spiral sculpture is, as mentioned above, so high for both species, that a correct determination based on spiral sculpture alone is not possible.

S. excelens is known from the northwestern reefs of New Caledonia and from Banc Eponge (southeast off New Caledonia) (SMIB 10). Bathymctric range alive in 205-545 m. Living on rubble bottoms.