Shell brittle, transparent, conic in form, whorls quite convex, suture broad. Very typical sculpture made by two spiral little cords placed at the periphery of last whorl. Another one is present immediately below suture. Sometimes there are present other spiral streakings fine, on last whorl. Aperture roundish in form, lip thin, culumella arched with a narrow umbilical crack. On last whorl chromatic pattern is made by four series of maculae brown in colour, quadrangular, equidistant, one of which below suture, two of which mounting periphery and one of which, less evident, at the base, all that on a ground yellowish in colour. Apex is prominent and it shows a sculpture made by about four rows of small papillae aligned. Crisilla chiarellii Cecalupo & Quadri, 1995, is a rather similar species. It is recognizable due to its larger sizes, to a different conformation of whorls, to a different ratio height/width, to a different height of last whorl and to a different form and sculpture of protoconch. Average measures of adult specimens are around 1.5 mm in height.
This species had been placed in the genus Setia by Ponder (1985), but we agree with Oliverio et al. (1986) thinking genus Crisilla is properer due to its evident spiral sculpture.

Crisilla beniamina is washed ashore in small numbers at many localities in the Mediterranean. West-Mediteranean France, Italy, Sicily, Tunesia. Eastern-Mediteranean Cyprus, Rhodos.

Habitat: it lives on bottoms rich in algae in the infralittoral and circalittoral zones. Distribution: it is collected in several areas of the Mediterranean. Locally common.

The length of seemingly full-grown shells varies from 1.2 to 1.7 mm. Fresh shells without periostracum are transparent, with a yellowish hue. The top whorls are of the same transparency and colour as the lower ones, or slightly more whitish. There often are tour spiral rows of darker spots on the body whorl. The lowermost row, however, may be absent in part of the shells. There always are about two close-set, narrow and week spiral ridges on the body whorl as a continuation of the suture. Another ridge is often present at a short distance below the suture. Occasionally, the body whorl may be entirely or partly covered with numerous extremely week spiral striae in addition to the sculpture just described. The shells are not very solid. There is no labial rib, nor does the aperture show any other peculiarities. Large specimens have about 5,2 whorls. The umbilical chink is week or absent. The dimensions of the apex vary: d = 0.09-0.11 mm; D = 0.17-0.20 mm. Seen from aside the nucleus is very prominent and circumscribed by a deep suture. Seen from aside in another position, the nucleus and first 1/4 whorl form a high segment of a sphere. At a magnification of 40 x , the surface of the top whorl is frosted, but without manifest sculpture. On the remainder of the protoconch, this frosted surface may merge into about 3-5 rather distant and somewhat irregular spiral lines which consist of numerous fine papillae. In many shells, however, this sculpture seems to be absent, probably worn away.