Diagnosis. Small (adult length 8.8 to 12.5 mm), breadth/length 0.37-0.43, aperture/total length 0.37-0.42, fasciole weak or absent. Suture shallow, subsutural region concave, adpressed to previous whorl; periphery with angular, node-like axial ribs, in t/s sharp, feeble where they cross subsutural concavity, evanescing at about level of parietal nodule; 8-10 per whorl; rostrum with 5-6 declivous spiral ridges. Surface highly glossy, superficially without microsculpture, but with extremely fine axial striae and even finer spiral striae. Terminal varix rounded, close to lip. White with a broad dark reddish-brown band around middle of last whorl, which often has a row of small whitish spots or dots towards base, subsuturally tinged with grey, lower edge of subsutural concavity with a distinct spiral brown line; concavity immediately behind anal sinus with a dark brown blotch, columella white.
Description. Small (adult length 8.8 to 12.5 mm); claviform, breadth/length 0.37-0.43, aperture/total length 0.37-0.42, whorls strongly concave posteriorly, with somewhat cylindrical last whorl and broadly tapering base, fasciole weakly convex or absent; siphonal canal squarely truncate, very shallowly indented. Outer lip in side view convex, with anal sinus asymmetrically U-shaped, directed adapically, parietal nodule large, stromboid notch moderately deep.
Suture shallow, subsutural region concave, rising high up base of previous whorl, adpressed. Periphery with angular, node-like axial ribs, opisthocline, in t/s sharp, subequal to intervals, feeble where cross subsutural concavity, evanescing at about level of parietal nodule; 8-10 per whorl. Rostrum with 5-6 declivous spiral ridges. Surface very glossy, superficially without microsculpture, but with extremely fine axial striae and even finer spiral striae. Terminal varix rounded, close to lip.
White with a broad deep reddish-brown band around middle of last whorl (showing weakly above suture on spire whorls), this band often bearing a row of small whitish spots or dots at its anterior third, sometimes merging into a spiral band immediately behind lip; subsutural concavity with a grey tinge and its lower margin has a distinct spiral brown line; base white. Protoconch and columella white, parietal nodule brownish-white; subsutural concavity immediately behind anal sinus with a dark brown blotch. Protoconch cylindric-domed, of two nearly smooth whorls, except narrow zone of micropustules along abapical suture. Posteriormost 1/4 of whorl with very fine incremental slightly arcuate lines, and 1/8 of whorl completely covered by micropustules and with very thin spiral line along abapical suture. Diameter about 700 µm, height about 670 µm. Protoconch-teleoconch transition indistinct, marked by disappearance of micropustules and spiral line and appearance of strong axial rib.
Measurements. Holotype: 12.1 x 4.7 mm. Largest and smallest adult paratypes: 12.5 x 4.5 mm and 9.3 x 3.8 mm, respectively.

Clavus delphineae resembles the vidua morph of C unizonalis in miniature (maximum length ca 12 mm, against ca 22 mm), or (more closely) the similarly small C protentus Hervier, 1896, but is distinguishable at a glance by its very high gloss. It further differs in its extremely minute growth lines and spiral striae, and in whorls that are adpressed at the suture, not separated by a narrowly notched suture that undercuts the succeeding whorl; the entire base of the last whorl is pure white (brown to off-white in those two species). It shares the brown spiral line and pale parietal pad of C protentus, but lacks its subsutural brown blotches.
According to material in the Dautzenberg collection (IRSNB), C delphineae was the species recorded from New Caledonia as Drillia mediocris (Deshayes, 1863) by Bouge & Dautzenberg (1914). Deshayes' poor figure shows suture-to-suture axial ribs, without a tubercular periphery or a sunken subsutural area, quite unlike the present species. The unique type of Pleurotoma mediocris, originally in the Maillard collection, cannot now be located; nothing agreeing with it appears to have been collected at the type locality (Reunion Island) by recent collectors (J. Drivas, M. Jay), and the name should be treated as a nomen dubium.

New Caledonia, Loyalty Islands and Coral Sea, 3 to 30 m, live specimens to ca 20 m.