Diagnosis: Shell cylindric-fusiform, occasionally biconic-fusiform, b/1 0.32, a/1 039; axial ribs low but distinct, except sometimes on back of last whorl; spiral lirae moderately thin, slightly flat-topped, half to one-third width of their intervals, 5-6 on penultimate whorl (plus one on subsutural cord), 12—13 on base of body whorl; intervals with microscopic spiral threads, 8-10 in shoulder furrow. Pale buff, tinged with light brownish orange, aperture edged with brownish orange. Protoconch breadth 0.75-0.85 mm. Length 6.0-12.3 mm.
Description: Shell cylindric-fusiform to slightly biconical, b/1 0.29-0.39, a/1 0.32-0.41, somewhat pupiform, with penultimate whorl nearly as wide as last one; teleoconch whorls up to 6, moderately convex with periphery just posterior to median; suture shallow, subsutural cord narrow but well-devloped, demarcated by a wide, shallowly concave furrow. Aperture rather narrow and almost linear, but constricted at entrance to siphonal canal; siphonal canal relatively wide, expanding slightly distally, oblique, not notched terminally; inner lip with moderately thin callus, microscopically rugulose anteriorly, its edge slightly free anteriorly but not forming a false umbilicus; columella slightly convex, meeting paries in a slight curve, most of parietal region occupied by a conspicuous pad formed by termination of outer lip; outer lip preceded by a wide, low, rounded varix, edge of lip sharp, not denticulate inside, in side view convex, anal sinus deep, apically rounded, asymmetrically U-shaped, with strongly constricted opening, stromboid notch deep.
Sculptured by widely-spaced spiral lirae, crossing low axial ribs, not forming distinct nodules; intervals with microscopic spiral threads, 3-4 between main spirals, 8-10 in shoulder furrow (an occasional thread stronger than others); growth lines coarse. Axial ribs rather straight, opisthocline, in t/s rounded, equal to intervals or wider than them, developing mainly in peripheral region, not reaching subsutural cord, evanescing below parietal level and sometimes on back of body whorl; 11—13 on 1st teleoconch whorl, 13-16 on last. Spiral lirae: subsutural ridge with single angular lira, other lirae somewhat flat-topped, half width of their intervals or less; 1 st whorl with 2-3 lirae between suture and subsutural groove, 5-6 on penultimate whorl; base of body whorl with 12-13 spiral lirae, becoming progressively weaker and closer anteriorly.
Protoconch bluntly conical, about 3 whorls; protoconch I worn, rest somewhat convex, smooth, except for 2 strongly opisthocline riblets near termination; breadth 0.75-0.85 mm, height 0.63-0.75 mm (b/h 1.13-1.19).
Dimensions: 6.5 x 2.3 mm (holotype); 12.3 x 4.8 mm, 6.0 x 2.2 mm (largest and smallest adult examples examined).
Colour whitish buff, tinged with brownish orange, aperture rimmed with darker brownish orange.

Notes: The presence of interstitial spiral threads distinguishes Thelycytharella oneili from all its previously described congeners, except for T. timorensis (Schepman, 1913) from Timor; the latter species has fewer main spiral cords (only II on last whorl, instead of 17-19 as in oneili), more conspicuously nodose spiral lirae and a shallower, less rounded anal sinus.
Notwithstanding this, the material referred here to oneili varies so much in proportions and adult size, that the five specimens examined might be taken to represent as many as three different species. Although all appear adult (prelabral varix fully developed), whorl number ranges from 4 to 6. One (Figs 3-4) closely resembles the holotype; another (Fig. 7) is much larger (length 12.3 mm, against 6.0-6.5 mm) and more biconic, with a slightly more conical protoconch. The remaining two (Figs 5-6) are markedly narrower (b/I 0.29-0.31 instead of 0.35-0.39) and are intermediate in size. However, in sculpture and other details they agree well, and as all these samples were dredged at similar depths, on a similar substratum, in the same general area, I have little doubt about their conspecificity.

Distribution: South Africa. Zululand and northern Natal, empty shells in 50-150 m, mostly on mud.
Additional material (all NMSA: NMDP, empty shells): ZULULAND: off Leven Point, 50-60 m, mud (E5857); off Port Durnford, 152 m, mud, stones (E5630). NATAL: off Sheffield Beach, 70 m, muddy sand (E9309); off Mgeni River, 96 m, sand, solitary corals (S655).