Shell elongate-fusiform, length 6.1 mm, length: width ratio 3.0 (including protoconch), aperture length about half shell length (49%). Protoconch 0.42 mm wide at base; 0.5 mm high, smooth, but too worn to see microsculpture. Teleoconch 5.0 whorls, spire slightly convex, stepped at sutures. First postnuclear whorl with about 15 axial ribs and 4 spiral cords; spiral cords increase to 6 (ventrally) to 8 (dorsally) on penultimate whorl and 21 on body whorl. Axial ribs 23 on penultimate whorl and 25 on body whorl. Intersections of cords and ribs raised as smooth pustules. Intercordal spaces narrower than cords, except at level of columellar folds. Microsculpture of fine axial riblets in intercostal and intercordal spaces, average spacing 4 (im, obsolete (or worn) on pustules. Aperture narrow, slightly wider anteriorly, sometimes with slight posterior depression below suture reminiscent of turrid notch. Outer lip barely undulated by spiral cords outside, with 10 denticles inside, anterior most denticles defining start of siphonal canal. Columellar folds 4, interior of aperture without lirations. Siphonal canal open, not recurved, siphonal notch wide.
Ground color white, first 2 teleoconch whorls pale pink, protoconch white. Some pustules near periphery brighter more opaque white, some aligned in groups of 3 or 4 on ribs or cords.

Although this species is known from only a single specimen, we decided to name it as it cannot be confused with any other Thala species; having a stronger resemblance to some species of Mitromica such as M williamsae Rosenberg & Salisbury, 2003 with its pale ground color and smoothly curving contours. The species is, however, clearly a Thala, having the episodic growth marked by internal varices; the remaining denticles of one varix can be seen through a bore hole in the spire. Among Thala species it is most similar to Thala milium (Reeve, 1845) from Japan, from which it differs in having a white rather than brown shell and a narrower, more sinuous aperture with stronger denticles that constrict the aperture opposite the first columellar fold. Thala malvacea Jousseaume, 1898 , which is known only from Djibouti and Yemen (Dekker & Turner 1996), is larger than Thala pallida: the 3 syntypes in MNHN measuring 9.5, 9.9 and 10.5 mm (vs. 6.1) and have first teleoconch whorl about 0.57 mm in width, vs. 0.46 mm; also the aperture is not as constricted in T. malvacea.
Thala kilburni is also known only from a single sample collected at Bassas da India, but it is has much coarser sculpture than Thala pallida. Strangely, there may be a third species of Thala at Bassas da India, known only from a single juvenile worn specimen (NMSA L472), collected with the type material of T. kilburni. It is more similar to T. pallida than T. kilburni, but seems to have a wider siphonal canal than either.

Type locality: Interior of lagoon, Bassas da India, French Overseas Territory, Mozambique Channel. Known only from the type locality.