Mitra carbonaria: Shell up to 70 mm (about 3 inches) in length, fusiformly-elongate to elongate-ovate, moderately solid. Whorls 6-8 apart from protoconch of 2-3 glassy-fawn, depressed nuclear whorls; spire whorls slightly or distinctly convex, sutures distinct but tight, irregular and occasionally weakly jagged. Spiral sculpture consists of shallow and usually minutely punctate spiral grooves and numerous, tightly packed, macroscopic longitudinal striae; spiral striae number up to 25 on the penultimate and up to 30 on the body whorl, striae usually obsolete in the centre of the body whorl, some individuals with the last 3-4 whorls almost smooth. Aperture slightly shorter or longer than the spire, moderately narrow and smooth within; outer lip only moderately thickened and simple. Lower half of columella weakly calloused and with 4-5 oblique folds, siphonal fasciole straight, siphonal notch distinct. Dark tan to blackish-brown in colour, su-tures occasionally finely spotted or narrowly lined with white, especially in young specimens; some individuals, particularly of the southern form badia, may have a few brown spiral lines. Interior of aperture brown or greyish-brown, parietal wall brown, columellar folds cream, fawn or occasionally flushed with light orange-brown; albino specimens are uniformly white under a yellowish-brown periostracum, but some intermediate specimens have a broad, light brown band on the sutural half of the body whorl.

Mitra nigra: Having examined various populations of M. cornicula and M. nigra, we suspect that M. nigra is the East Atlantic form of the Mediterranean-Adriatic M. cornicula. Although large, inflated specimens, with the typical blackish-brown exterior colouring and bluish-white aperture and columellar folds, are easily separated from the smaller, horny-brown M. cornicula, there are numerous individuals from the Canary Islands, Madeira and Cape Verde Islands which are intermediate in characters between M. cornicula and M. nigra, and specimens from the same lot could be assigned to either species. Fischer (1942) pointed out that M. nigra is similar to M. cornicula, but that the former species has 1 more columellar fold; we found the normal fluctuations of ±3 folds in both species. M. nigra has also been reported from the South of France by Monterosato (1877) and from Algeria by Pallary (1900); these records may have been based on larger examples of M. cornicula.
In its typical form the shell is larger than M. cornicula, the sutures are slightly ledged, the whorls more inflated particularly at the body whorl, and the sculpture consists of few or numerous, fine and sometimes uncountable spiral striae and macroscopic axial hairlines. The colour is light tan to brown, overlaid by a dark brown to blackish-brown periostracum, and some individuals may have a pale band at the sutures; the aperture is bluish-white, bluish-brown or purplish-violet and the columellar folds are white or violet. The largest specimen seen measured 46.0 mm in length.

Mitra carbonaria: This common, temperate water Austral-Neozelanic species is very variable in size, shape, sculpture and colour, and consequently has received a host of specific names. The occurrence of numerous intergrades between the various forms, currently recognized as "species", forces us to consider them as sympatric forms and ecophenotypic variants rather than allopatric subspecies or valid species. Two various forms of M. carbonaria are briefly discussed:
- rhodia form: a slender, very small and often immature form, which occurs throughout the dis-tributional range of the species and is more frequently collected sublittorally; this form is also moderately common in New Zealand, at depth from 10 to 17 fathoms.
- badia form: this is the short, broad and smaller form of M. carbonaria which is more frequently encountered from Victoria to West Australia. The species subsequently described as M. castanea A. Adams, and M. rosettae Angas, represent the broad form. Sowerby (1874), Hedley (1913) and Cotton (1957) synonymized M. badia with M. carbonaria, but Hedley (loc. cit.) specifically separated M. rosettae on the basis of the variable sculptural features of more wide-spaced spiral grooves.

Mitra carbonaria: West Australia to S.E. Australia, New Zealand and the Kermadec Islands. In coral sand, shell-debris and mud, under rocks, from the intertidal zone to a depth of 21 fathoms.

Mitra nigra: Bay of Biscay to the Azores, Canary Islands and Angola, West Africa.