Mitra, LAMARCK, 1798

GENUS MITRA LAMARCK, 1798 View in CoL

( FIGS 9, 10A)

Type species: Voluta mitra Linnaeus, 1758 , by tautonymy.

Synonym: Tiarella Swainson, 1840 . Type species: Voluta papalis Linnaeus, 1758 ; SD ( Gray, 1847) Papalaria Dall, 1915 . Type species: Voluta episcopalis Linnaeus, 1758 [= Mitra mitra (Linnaeus, 1758) ]; SD, Coan (1966: 131).

Diagnosis: Shell medium sized to large (50–170 mm), thick-walled, fusiform or elongate-fusiform, with truncated base and colour pattern of multiple rounded or squarish red spots or bands on white background. Protoconch multispiral, of about three smooth slightly convex whorls. Suture deeply impressed. Teleoconch whorls gently convex or angulated adapically, bearing a row of short spiny bumps at shoulder. Rest of whorl surface sculptured with weak, evenly spaced, spiral grooves, well pronounced on early spire whorls and often vanishing later. Siphonal canal very short with robust siphonal fasciole delineated from shell base by deep depression. Aperture rather wide, with deep siphonal notch; outer apertural lip nearly straight adapically and strongly convex in its lower portion, bearing numerous fine denticles throughout its length or limited to its abapical margin. Inner lip reflected, with three to four subequal oblique columellar folds. Radula with rather narrow rachidian bearing six subequal cusps, and very wide laterals bearing cusps throughout their width ( Fig. 10A). Cusps rather strong near rachidian and becoming progressively weaker laterally.

Distribution: Indo-Pacific, shallow intertidal and subtidal to upper bathyal depths, sand and rocky bottom.

Species included: Mitra mitra (Linnaeus, 1758) 1, Mitra deprofundis Turner , 20013, Mitra papalis (Linnaeus, 1758) 1, Mitra stictica (Link, 1807) 3.

Remarks: A critical reassessment of the contents of the genus Mitra is one of the main outcomes of the present study, and our phylogenetic analysis demonstrates that the name Mitra may be confidently applied to a handful of species only. The redefined genus Mitra is morphologically distinctive because of the conservative shell shape with rather high spire and low aperture, presence of denticles on the outer aperture lip and a recognizable colour pattern. At the same time, its radular morphology is overall the same as in many other mitrid clades and adds little to the diagnosis of the genus.

Quasimitra cardinalis and Q. puncticulata resemble species of Mitra . However, Q. cardinalis has a notably wider shell with lower spire, and Q. puncticulata lacks the characteristic colour pattern of Mitra and bears no denticle on the outer aperture lip. Nebularia incompta also resembles Mitra in shell proportions and the presence of denticles on the margin of the outer lip, but has a stronger sculpture and its siphonal canal is not clearly delineated from the shell base; besides, it has a typical Nebularia - type colour pattern instead of a Mitra - type. Some Strigatella species, especially S. imperialis , also closely resemble Mitra in the morphology of the abapical part of the shell (aperture and siphonal canal), but they have a notably lower spire and lack the Mitra - type colour pattern as well.