Shell small, fusiform to turriform, with tall spire and elongate aperture (w/h 0.24-0.30; a/h 0.39-0.45). Protoconch pointed, very high, with three or more adpressed whorls (almost always broken or eroded). Teleoconch whorls evenly convex to slightly adpressed in outline, sculptured with very strong, widely set, orthocline ribs, in their adapical third intersected by one or two faint spiral grooves succeeded by a weak rounded cord. Spiral sculpture usually absent on the periphery of the last adult whorl, but regular grooves present on shell base and siphonal canal. Siphonal canal moderately long, tapering, widely and shallowly open. Aperture elongate, its inner lip with three strong, widely set, obli¬que, columellar folds. Shell colour off-white, often with remains of brown periostracum. Apex usually strongly corroded. Radula rachiglossate, about 1 mm long and 0.25 mm wide, consisting of 45+ rows. Rachidian rather narrow but base robust and strong, cusps short and blunt (in the specimen from Taiwan, the central cusp was bifurcated at its tip - a feature we consider to be individual), medial projection not pronounced. Lateral teeth unicuspidate, widely sickle-shaped, robust in appearance.

AS Tongsuapusia duplex
Shell solid and median in size, about 16 to 41 mm, elongate fusiform. Protoconch of 2 slightly mamillate whorls, teleoconch of 7 to 10 flat-sided convex whorls. Sutures are distinct. Sculpture with widely spaced, ele¬vated, slender axial ribs and fine spiral striae. Axial ribs numbering 15 to 17 on the penultimate and 5 to 17 on the body whorl. Subsutural spiral cord develops in the first teleoconch whorl, splits consequently to two to five rows of flat cords bearing the same strength of maternal cords and by bisecting low nodules on axial ribs give the appearance of a duplicated sutural girdle; lower half of the body whorl with 15 to 25 slightly granulose cords. Aperture is narrow, shorter than spire height and smooth within. Outer lip is thin, simple and gently convex and be¬comes wider and upward angulate at maturity. Shell base gently convex and a callus pad on parietal wall. Collumella bears 3 oblique folds and a siphonal fasciole, obso¬lete. Siphonal canal is short, narrow and straight and siphonal notch is inconspicuous. Color creamy white, pale yellowish or fawn; some shells are ornamented with three narrow brown bands, one below subsutural cords, one at mid-portion and the rest at inferior portion of whorls. Periostracum is faint straw-colored.
The radula (Text figs. 1-2) from a 37.16 mm shell (Plate 1, Fig. 4) is typically Pusiine with a tricuspid rachidian. The radula is about 1.34 mm in length (3.28% of shell height and 7.88% of aperture height), 0.15 mm in width (0.37% of shell height and 0.88% of aperture height) and consists of about 64 rows. The rachidian tooth, with a strongly curved anterior margin and long lateral flap on a broad arched posterior base, bears three short sharp cusps. Cusps are triangular, closely spaced and emanating from anterior edge of the basal part with the central cusp being longest and widest. Lateral tooth is unicuspid, subtriangular with curved and blunt tip on a wide base.
Both epithets of Mitra simplicissima Schepman, 1911, and M. simplicissima var. glabra are primary homonyms of M. simplicissima Cooper, 1894, and M. glabra Swain-son, 1821. The holotype of M. simplicissima is in the Zoological Museum Amsterdam and with dimensions of length 21.6 mm, width 6.3 mm, and height of aper¬ture 10.8 mm. The holotype of M. simplicissima var. glabra, is in the same Institution with dimensions of length 16.4 mm, width 5.5 mm and height of aperture 8.1 mm (Cernohorsky, 1982).

Our material displays considerable variation in shell proportions and details of shell sculpture. The specimens collected in the South China Sea are morphologically very close to the typical form, as well as to the holotype of Vexillum pratasense, as illustrated by Lan (2004). Their shells are wide, fusiform, with spiral sculpture limited to the adapical portion of the whorls and to the siphonal canal.
Specimens from the Solomon Sea here assigned to Tongsuapusia duplex vary in proportions from wide and fusiform - similar to those from the South China Sea - to usually more slender, with a taller spire and more widely set axial ribs. Examination of 25+ specimens from the Solomon Sea shows that shell proportions, strength of axial ribs, and extent of spiral sculpture vary continuously, and are not strictly correlated: wide fusiform specimens may have fine ribs and well-pronounced spiral sculpture, and elongate turriform specimens may have strong, widely spaced axials with very weak spiral elements. We are inclined, therefore, to consider all these forms to represent a single variable species. Among Tosapusia species, typical Tongsuapusia duplex is most similar to Tongsuapusia bismarckeana, Tongsuapusia myurella sp. nov., and Tongsuapusia turriformis ; however, it can be readily distinguished from all of them by the shell proportions (even taking into account the observed intraspecific variation in Tongsuapusia duplex), shape of the last adult whorl and sculpture details. Tongsuapusia bismarckeana has a longer siphonal canal and finer and narrower opisthocline ribs than in Tongsuapusia duplex. By contrast, Tongsuapusia myurella and Tongsuapusia turriformis have turriform shells with a higher spire and flattened whorls profile; the shell base in both of these species is notably shorter than in Tongsuapusia duplex, so the last adult whorl is constricted to the siphonal canal and looks somewhat inflated. Finally, shell proportions, a strong axial sculpture, and weakly developed spiral elements in Tongsuapusia duplex resemble the genus Latiromitra; however, unlike Tosapusia, species of Latiromitra have very weak columellar folds and possess an operculum, even though it is often reduced.

Distribution and habitat
Indonesia, South China Sea, Papua New Guinea, Solomon Islands. Soft bottoms, depth range 503-814 m.