Description. Shell fragile, minute, translucent, oval-conical, up to 1.2 x 0.7 mm . Protoconch smooth, dome-shaped (typical of the genus), whorls 1.25, diameter 280 um, separated from the teleoconch by a clearly visible line. Teleoconch with 2.5 to 3 inflated, rounded, strongly convex whorls; whorls with regular contour and conspicuous increase in width. Spire moderately high. Sculp¬ture absent, except for very fine, inconspicuous growth lines. Suture deep, constricted. Last whorl large, globose, 70-75% of shell length. Base large, rounded. Aperture oval, oblique with continuous peristome, adapical angle somewhat acute. Parietal region thin, very slightly convex. Outer lip with very thin edge . Inner lip thin, very slightly recurved over umbilicus. Umbilicus a very narrow fissure. Animal light-yellow with dark-brown blotches visible at transparency. Operculum simple, thin, nucleus eccentric, yellowish at transparency.

Setia alexandrae sp. n. is distinguished from the other Azorean congeners by its smooth, transparent to translucent shell, and yellowish animal having light to dark-brown blotches over the entire body. Setia alexandrae sp. n. lacks any colour decoration/pattern on the shell. Colour is a distinctive feature of most of the known Setia (e.g., variably coloured flames, spots or vertical lines, sometimes interrupted medially), which are so abundant on the Azorean Setia subvaricosa Gofas, 1990, S. amabilis (Locard, 1886), S. ambigua (Brugnone, 1873) and S. scillae (Aradas & Benoit, 1876). Setia lacourti (Verduin, 1984) is similar in size (up to 1.2 mm in length) and also lacks any coloured pattern on the shell; this species was reported from the Azores by Segers (2002: 89) as Setia cf. lacourti. Setia alexandrae sp. n. clearly differs from S. lacourti in shell shape (more elongated on the first, flattened on the latter). Setia ambigua was also reported from the Azores (Hoenselaar and Goud in litt. 2002, Avila et al. 2012), from Terceira Island (Praia da Vitoria, 38°43'N, 27°04'W, sandy beach). Setia alexandrae sp. n. differs from S. ambigua by being about 50% smaller and by lacking any coloured decoration on the shell. A very similar specimen to Setia alexandrae sp. n. was recently found in the Pleistocene record of Santa Maria Island, Azores (Prainha outcrop, bed Bl of Avila et al. (2009a); latitude 36°57'3.05"N, longitude 25°6'44.20"V/). This well-preserved juvenile shell is herein reported as Setia cf. alexandrae DBUA-F 137/151-4 (0.61 x 0.40 mm). The protoconch and teleoconch shape and sculpture are identical to Setia alexandrae sp. n., as is the shape of the aperture. However, as it is a juvenile specimen we prefer to treat it as Setia cf. alexandrae until adult material is examined.

Habitat. On rocky shores covered by algae, from the intertidal down to 20 m depth. Type locality. Santa Cruz, Graciosa Island, Azores.
Geographical distribution. Pico, Graciosa, Sao Miguel and Santa Maria Islands, and Formigas Islets. Probably endemic to the Azores.