Shell large for genus, 26 mm, heavy, high spired with spire reaching a sharp point. Protoconch of 2 small, rounded, smooth whorls. Teleoconch up to 10 whorls. Suture impressed. Upper whorls have row of 8-9 pointed nodules just below midpoint of whorl which give shell a turreted appearance; in some areas these may form short spines. Last nodule on body whorl extends down whorl as a varix, behind outer lip. Below nodules on body whorl is a row of low secondary ribs. Outer lip thin, serrated, stromboid notch prominent. Sinus deep, channeled with prominent callus. Columella straight, thin, slightly callused. Anterior siphonal canal short, broad. Aperture deep, subrectangular. Colour off-white, aperture glossy white. Queensland specimens may be completely off white or have a broad, light brown band across top of body whorl. In shells from New Caledonia the general colour is light brown, while those from Mauritius have a broader band interrupted by about 16 low, white ribs.
Radula: Typically drilliine, with one central tooth on each side flanked by one marginal. Central tooth small, flat, leaf shaped, base 45 mu wide, broadening to 67 mu, before tapering to centre. Narrow ridge down entire surface of tooth extends into a point beyond flat part of tooth. Marginal teeth crescent shaped, 365 mu wide, tooth itself reaches maximum height of 55 mu. Series of up to 16 sharp spines on front of each tooth, increase in size until near centre of radula, maximum height 65 jim, final two or three spines smaller. Marginal teeth long, flat slightly curved blades, up to 630 mu long, 70 mu wide, with strong ridge along middle of outer part of tooth.
Operculum: Brown, horny, flattened on columellar side, rounded on outer side, with tine growth lines over surface, nucleus nearly terminal. 6.3 mm long in a 28.6 mm shell.

Description (New Caledonian population): Shell thick, broadly claviform (breadth/length 0.45-0.49) with sharp, initially coeloconoid spire, apex often somewhat stiliform; suture between later whorls fissure-like (partly recessed under edge of succeeding whorl); fasciole strong, with distinct false umbilicus; aperture oblong-ovate, aperture/total length 0.40-0.47), outer lip slightly alate, base wide, oblique, shallowly indented. Outer lip slightly prosocline, gently curved, strongly serrated, stromboid notch very deep, anal sinus U-shaped, directed slightly adapically, parietal pad forming a large tubercle; base of columella curved to right, forming a small, often sharp basal projection.
First 2-3 whorls rather flat-sided, with suture-to-suture axial ribs; thereafter, the latter become progressively weaker subsuturally and more tumid basally. Later whorls with subsutural region rising high up preceding whorl, flattened, becoming concave above shoulder; shoulder sometimes defined by a low ridge with sharply incised adapical edge, which bears a series of nodules that similarly terminate abruptly above at border of sulcus; in others they are evenly rounded; on latter part of last whorl the nodules occasionally form secondary extensions that cross to suture. Nodules rounded or squamiform (often in same individual), 12-14 on penultimate whorl, in t/s angularly rounded or rounded-angular to spathulate (when strongly squamiform), with sloping sides, mostly subequal to intervals, base of nodules rapidly evanescing above last suture. Early whorls with seven straight, almost orthocline ribs per whorl. Varix moderately strong, roundly angular, shouldered posteriorly, evanescing anteriorly. Base of last whorl with a series of faint spirally arranged bumps, strengthening towards back of lip into 3-7 rows of low nodules; rostrum with 7-9 rounded spiral ridges. Entire surface covered with dense, wavy microscopic spiral striae, collabral threads coarser and irregular.
Uniform greyish- or yellowish-white, sometimes with a broad, faint band of pale buff around middle of last whorl; columella and lip white, interior of aperture yellowish; apical whorls evidently brown.
Protoconch rounded conical, somewhat cylindrical, of two smooth whorls, diameter about 660 µm (one example only).
Measurements. 26.6 x 13.9 mm (largest adult); 24.7 x 11.7 mm (smallest adult).

Shell thick, broadly claviform with sharp, initially coelo¬conoid spire, and fasciole strong, with distinct false umbilicus. First 2-3 teleoconch whorls rather flat-sided, with very low suture-to-suture axial ribs; there¬after, axials progressively weaker subsuturally and more tumid basally. Later whorls strongly shouldered, with strongly concave adapical region. Shoulder at about mid-height of whorl, marked with prominent nodules, rounded, or sometimes weakly squamiform on late whorls. Base of nodules rapidly diminishing above last suture. Microsculpture of dense irregular collabral growth lines, well pronounced on adapical regions, very fine spiral striae on base of whorls. Shell base with wide, irreqular spiral folds, qivinq it somewhat crumpled appearance. Aperture oblong-ovate, outer lip slightly alate, base wide, oblique, shallowly indented. Outer lip slightly prosocline, strongly serrated, stromboid notch very deep, anal sinus U-shaped, directed slightly adapically, with distinct parietal pad. Background colour yellowish-white, with broad, orange or light-brown band around middle of last whorl; columella and lip white, interior of aperture yellowish.

C. exasperatus is similar to C. canalicularis but is thinner, with a higher spire, and much shorter spines. The secondary ribs which are present on the body whorl of C. exasperatus but not C. canalicularis are a key feature in separating the two species.

As was observed by Wells (1991), Clavus exasperatus shows a certain amount of geographical variation. The New Caledonian population, although characteristic, is not here recognised as taxonomically distinct, although a full description of this material is given above. Typical New Caledonian individuals differ from typical examples of C exasperatus (the probable holotype in the NHMUK most closely resembles the Indian Ocean population) in having peripheral nodules that are sharply cut adapically and are usually more or less squamiform, a base that lacks axial sculpture and is completely smooth in immature shells (in exasperatus it bears the tapering bases of the axial ribs, usually with vermiculate threads interpolated). Nevertheless, apparently intermediate individuals also occur in New Caledonia: these have rounded peripheral tubercles, and axial ribs with basal extensions and weak interpolated riblets. New Caledonian individuals are always off-white except sometimes for a faint buff zone, never dark brown or with streaks of brown as in the type and similar specimens from other parts of Indo-West Pacific, and the tooth-like base to the columella callus is absent or indistinct in the latter.

Clavus exasperatus as circumscribed herein can be differentiated from its congeners in the C. canalicularis complex by the combination of nodules situated about mid-height of late teleoconch whorls, presence of wide rounded folds, and a brown spiral band on the shell periphery. Similar features are displayed by C. groschi, but the latter species possesses oblique, axially elongated nodules with rather sharp crests, whereas C. exasperatus has rounded nodules, typically squamiform at late whorls.
The results of our phylogenetic analysis reject the previously accepted concept of widely distributed and variable Clavus exasperatus, which has long been established in the literature (Tucker 2004; Kilburn et al. 2014). Our results suggest that C. exasperatus is actually a western Indian Ocean species, although its eastern range limit is uncertain due to the paucity of sampling efforts along the African Coast and in the central Indian Ocean. Nevertheless, based on this contraction of the C exasperatus distribution range, previous records of this species from the Indo-West Pacific need to be critically re-evaluated. We are unable to unequivocally place the specimen figured by Hasegawa ef al. (2000: plate 309, Figure 8), into one of the species recognised herein, due to the poor condition of the shell. The specimens illustrated in Philippine Marine Molluscs Vol. 2 (Sysoev 2008) certainly represent C. davidgilmouri n. sp. - see synonymy of the latter species. Finally, it is most likely that Pleurotoma exigua from Torres Strait off Queensland is not a synonym of C. exasperatus as circumscribed herein, but is actually a different species, possibly one of the species dealt with in the present paper. Due to the loss of the type specimen, ascertaining the iden¬tity of Pleurotoma exigua is virtually impossible; we are unable to assign this name and consider that describing a new species is a more justifiable option.

Indo-West Pacific; south in eastern Queensland to Townsville.

Distribution. Japan and Hawaii to New Caledonia, Loyalty Islands and Solomon Islands, west to Djibouti, Mauritius and southern Mozambique, in sand or stones under and between dead coral, low tide to about 31 m (elsewhere to 75 m).

Mozambique, Madagascar.