Diagnosis: Shell moderate to depressed, whorls strongly angled at shoulder and periphery; sculptured by spiral cords and axial pliculae; shoulder without or with only very weak spiral sculpture; axial pliculae strongest on shoulder, base corded. Umbilical margin angular, usually pliculate. Colour, orange-pink apically, metallic when fresh, white to cream below.
Description: Shell moderate to depressed (L/D - 0,51-0,67), spire prominent, stepped, nearly evenly conical; whorls strongly angular at shoulder and periphery; shoulder normally horizontal, sometimes sloping down to shoulder angle, very occasionally sloping down to suture (SAM A5268); periphery at or just below mid-whorl; early whorls not angular; teleoconch of up to 5 whorls. Sculpture of relatively fine spiral cords and axial pliculae; 4-6 cords at end of first whorl, similar but more widely spaced at end of second; weaker intermediaries arise during subsequent whorls; body whorl with 10-20 cords above and including periphery, often alternating in strength; shoulder generally without or with a much weaker spiral sculpture comprising a few fine lirae and occasionally one or two cords near shoulder angle; basal cords similar to those above, but those bordering umbilicus often stronger. Axial sculpture absent on first and second whorls; subsequent whorls with regular, relatively close set, curved axial pliculae; most obvious on shoulder becoming obsolete toward aperture where axial sculpture comprises only fine growth-lines; pliculae weak or absent at periphery becoming stronger toward umbilicus where they may cause distinct, close set granulation of spiral cords. Umbilicus wide, deep; margin usually angled, but not strongly so; interior with ca 6 spiral cords, occasionally also with lirae; axial pliculae sometimes stop abruptly at umbilical margin and interior sculptured axially only by growth-lines; sometimes pliculae confined to cord intervals or sometimes strong, crossing the cords and causing obvious granulation. Aperture five-sided, parietal side short; peristome incomplete; outer lip prosocline, smooth; interior nacreous.
Protoconch: Typically solarielline, diameter 400-420 µm.
Colour: Protoconch and early whorls yellowish-white to pale yellowish-pink; apical surface of remaining shell evenly coloured, yellowish pink to light reddish-brown; base white to yellowish-white. Apical surface of fresh shells with a metallic sheen and slight iridescence giving a copper-like appearance,
Dimensions: Holotype, length 8,0 mm, diameter 13,0 mm; largest specimen, length 8,8 mm, diameter 13,9 mm.

A deep-water species somewhat resembling I. undata (Sowerby, 1870). Indeed, Barnard (1963) referred PF specimens to the latter species. The present material, however, has a more strongly angled profile and fewer, stronger spiral cords between the shoulder and the periphery, which contrast sharply with the weak or absent spiral sculpture on the shoulder. In I. undata the spiral sculpture remains the same above and below the shoulder angle. The uniform pinkish-brown, almost copper-like colour of the apical surface in I. kilburni is also characteristic.
There is some variation in whorl profile, cord number and strength of umbilical pliculation. The single specimen from the Tsitsikamma coast is particularly unusual in being very depressed, having finer, more numerous spiral cords and reportedly coming from much shallower water. It closely resembles Margarita bicarinata Adams & Reeve, 1850, reputedly from "eastern seas”. For this reason it is not included in the type material or distributional data.

Distribution: South-Africa. Central Transkei to eastern Cape, 350-550 m (living specimens the same, but mostly over 400 m, muddy sand).