Shell thick, of medium length, up to 30 mm long. Whorls 6-7, protoconch eroded on all specimens examined. Spire narrow, with a row of nodules on the upper whorls. Body whorl moderately larger. Nodules on last two whorls elongated into long, low axial ribs with pronounced spines which do not extend to margin of outer lip. 5 to 7 spines on each whorl, broad at base, tapering, up to 9 mm long, but some specimens have very short spines. In some specimens edge of the spine is recurved almost to form a tube. Suture adpressed, with deep, U shaped sinus on shoulder of body whorl. Spiral striae below spines may be nodulose. Columella smooth, slightly convex. Aperture moderately wide, outer lip squarish, may have fine serrations. Anterior siphonal canal broad, shallow, stromboid notch narrower, distinct, posterior canal small, narrow. Colour off-white, broad brown band across middle of body whorl may be present. Band does not extend to outer lip. Band darker on upper part of whorl. Aperture white or tinged with yellow, which may also occur on outer shell. Brown band extends onto upper whorls as a line above suture. Lenth up to 31 mm. Width up to 17 mm

Biconic-claviform or broadly claviform with orthoconoid spire (breadth/length ratio varies greatly because of varying lengths of spines), and relatively wide aperture (aperture/total length 0.42-0.50). Teleoconch of six to 7.5 strongly shouldered whorls, subsutural region concave, adpressed to base of previous whorl. Suture narrowly undercutting succeeding whorl, irregularly undulating. Early spire whorls sculptured by wide axial folds forming nodules or sharp projections on peripheries; late 3-4 whorls with strong squamiform, sometimes nearly enclosed spines directed outwardly on peripheries, especially long on penultimate and last whorls. Shell base usually with single row of low, rounded nodules. Spiral sculpture indistinct on spire whorls; last whorl with rugose, sometimes gemmate cords, on parietal region; fasciole with 6-7 low rounded declivous cords. Axial sculpture of dense growths lines, forming sharp ridges in some specimens.
Aperture wide, anal sinus openly U-shaped, directed adapically, or V-shaped in immature shells. Parietal nodule large, stromboid notch distinct. Inner aperture lip heavily calloused, sometimes false umbilicus presents.
White, cream or uniformly pale, usually with a broad deep orange-brown zone at mid-last whorl. Protoconch dark yellowish-brown, contrasting with the white teleoconch whorls that follow.
Protoconch narrowly domed, of about 1.75 smooth evenly convex whorls, diameter about 750 µm, height about 630 (im. Protoconch-teleoconch transition indistinct, marked by weak arcuate axial rib. Protoconch in most specimens examined worn or missing.
Measurements. Largest studied specimen attains 48 mm length.

[Adapted from Kilburn et al. 2014] Shell robust, biconic-claviform or broadly claviform with orthoconoid spire. Protoconch narrowly domed, of about 1.5 smooth whorls. Teleoconch of 6 to 7.5 strongly shouldered whorls, subsutural region concave, suture narrowly undercutting succeeding whorl, irregularly undulating. Early spire whorls sculptured by wide axial folds forming nodules or sharp projections on peripheries about mid-height of whorl. Late whorls - 3-4 with strong squamiform spines directed outwardly on peripheries, especially long on penultimate and last whorls. Shell base smooth or with single row of low, rounded nodules. Spiral sculpture indistinct on spire whorls; last whorl with rugose, sometimes gemmate cords; fasciole with 6-7 low rounded declivous cords. Axial sculpture of dense growth lines. Aperture wide, anal sinus openly U-shaped, directed adapically, or V-shaped in immature shells. Parietal nodule large, stromboid notch distinct. Inner aperture lip heavily calloused. White, cream or uniformly pale, usually with a broad deep orange-brown zone at mid-last whorl, or uniformly light-brown.

Australian specimens examined all had a moderate body whorl and a width/length ratio of about 0.44 to 0.53. Some Western Pacific specimens are narrower, with shorter spines, making them similar to C. exasperatus. These specimens may still be distinguished as C. canalicularis by the spines on the last two whorls; while C. exasperatus has axial ribs, spines are never formed. In addition, C. exasperatus has a series of low, secondary ribs on the body whorl below the primary ribs. The syntypes of Pleurotoma auriculifera (Plate 2, Figure 9) also show the characteristic spines of C. canalicularis.

The only other New Caledonian species with similar (if weaker) spines is Clavus rugizonatus Hervier, 1896, which differs in bearing dense spiral rows of pustules, often diagonally aligned, on its base, and usually by the vivid orange-brown tint of its colour band. New Caledonian specimens of C. canalicularis usually have only a row of rounded tubercles around the middle of the base, and are white with a dark brown to dark greyish brown zone around the middle of the last whorl (rarely with a brown subsutural line). In colour pattern they resemble Clavus unizonalis (Lamarck, 1822), which, however, has a dark columella and lacks the spines. Among individuals of C. canalicularis, degree of development of individual spines varies, rendering breadth/length ratios almost meaningless.

The species shows wide variation in colouration, shell proportions and prominence of nodules / spines. It can be differentiated from other allied species by its squamiform sculpture elements, (which are diagnostic per se if they form spines), by shoulder situated at mid-height of the whorl, by lack of sculpture, or by prevalence of spiral elements on the shell base. Morphologically C. canalicularis is most similar to C. rugizonatus. The two species are sympatric in Papua New Guinea and New Caledonia, and can be differentiated by the lack of spirally aligned nodules on the shell base of the former species. Another clearly closely related species, unfortunately lacking from our phylogenetic dataset (and therefore not provided with a separate entry herein), is Clavus devexistriatus. Unlike C. canalicularis, the latter species possesses widely set striae, well pronounced throughout the height of last whorl. Furthermore, unlike all other species considered herein, C. devexistriatus displays a colour pattern with brown adapical portion of whorls, and cream-white or pale shell base.

Distribution
0-24 m, in subtidal sand patches in reef. Western Pacific; Australia: Darwin, Northern Territory to Townsville, Queensland. Other records: Cernohorsky (1972): Indo-West Pacific (including Fiji), Hinton (1972): Papua New Guinea. Springsteen and Leobrera (1986): Philippines.

Distribution. Fiji and southern Japan to Indonesia, Queensland and New Caledonia, west to N.W. India, In New Caledonia low tide to ca 70 m (32-67 m on Plateau des Chesterfield), usually in sand or sandy gravel among rocks or coral, in our material confirmed live specimens collected to ca 30 m.