Setia lidyae: — (1) The length of seemingly full-grown shells varies from about 1.1-1.4 mm.
— (2) Fresh shells are transparent, with a yellowish hue. The top whorls are of the same transparency and colour as the lower ones. There are usually four spiral rows of darker spots on the body whorl, the lower ones of which may be weak and vague. Occasionally, other colour patterns may occur.
— (3) There are always about four rather weak, equidistant spiral grooves on the basis of the shell. Moreover, there often are two narrow and weak spiral striae as a continuation of the suture, to the effect that the basis of the shell is covered by about six more or less equidistant spiral striae. These striae seem to be somewhat better developed among material from the Canary Islands than among Madeiran material. In well preserved shells extremely fine and close set, superficial spiral engraving may be seen just below the suture.
— (4) The shells are rather fragile. There is no labial rib. As in S. perminima the aperture is relatively large, with the columellar side almost in line with the parietal side.
— (5) Large specimens have about 3.7 whorls.
— (6) There is no umbilical chink.
— (7) The dimensions of the apex vary: d = 0.09-0.10 mm; D = 0.15-0.17 mm.
— (8) Seen from aside in position 1, the nucleus is little prominent, and circumscribed by a rather shallow suture. Seen from aside in position 2, the nucleus and first ¼ whorl form a medium high segment of a sphere with also a somewhat shallow suture.
— (9) At a magnification of 40 x , about 9
very fine, distant and equidistant spiral lines may be seen on the protoconch.

Shells here studied fragile, conical-oval, with something more than 3 convex whorls and up to 1.2 x 0.67 mm. Last whorl occupies 80% of height and the aperture is relatively large . There are some rather weak, equidistant spiral grooves on the basis delimiting wide, slightly prominent cords. There is a subsutural cord and, below, several cordlets only seen at high magnification. The sculpture is least noticeable in the central area of the whorls. Shells translucent, with a yellowish hue and whitish base . There are four spirals of reddish spots, the lower one more diffuse. Paucispiral protoconch sculptured with about nine parallel furrows which delimit flat cords. Near the nucleus, the furrows are not yet delimited, appearing as imperceptible incisions .

Setia lidyae: This species is very similar to Crisilla perminima, but constantly differs in the colour: there is no dark colour spot at the basis, the inner lip of the aperture is always colourless or of a light colour, and the spiral row of darker spots below the suture never merges into a spiral colour band. Moreover, the spiral sculpture on the basis of the shells is generally somewhat more developed. These differences are so consistent that I have no doubt that two distinct species are involved.
From Crisilla innominata the new species differs in the smaller dimensions, the absence of a labial rib, the more delicate spiral sculpture just below the suture, the ornamentation of the protoconch, and the form of the aperture.
From Crisilla beniamina the new species differs in the sculpture and form of the protoconch, and in the presence of spiral striae at the lower end of the basis.

VERDUIN (1988) described Setia lidyae only a few days after PALAZZI (1988) had described Alvania iunoniae. GOUD (1999) noted that both taxa corresponded to the same species, provided evidence for priority of the specific name given by Palazzi, but included it in the genus Setia. This species can be confused with C. spadix and C. perminima but differs from the first by having grooves in the protoconcha instead of spiral cords in addition by its different colour pattern. S. perminima also differs in the colour pattern of the shell, having wide brown-reddish bands instead of spots and dark colour in the inner lip of the aperture. Moreover, the spiral sculpture on the basis of the shells is generally somewhat more developed in C. iunoniae.

Setia lidyae: Madeira and Canary Islands.

Madeira, Selvagens and Canary Islands (Tenerife, Gran Canaria, Lanzarote and La Palma). Subtidal; some shells were found down to 60 m depth.