Shell conical, small, quite translucent but not totally transparent, apex slightly sharpened and aperture very large. Ornamentation or colour absent. Shells in preservative fluids become white and opaque. Profile straight, whorls convex, the last one very high, occupying 2/3 of the shell height Sutures clearly distinct by whorl convexity. The false suture is very evident as a fine opaque line located under the true suture. Both sutures are parallel and the space between them is very narrow. The growth scars are strongly marked. Normally there are two per whorl, located irregularly because the snail grows more than half a whorl each growth period. These scars are the only marks appreciated on the surface of the shell. The shells lack microsculpture in the teleoconch and protoconch. Some shells present the first whorls deeply eroded, probably due to chemical attack of the preservative fluids, indicating a greater debility of the larval shell with respect to the teleoconch. Mucronate protoconch of 2.5 whorls, without coloration or ornamentation that differentiates it from the teloconch.
Aperture large, oval, slightly sharpened at it upper part and rounded at the base. Outer lip faintly swelled at the tip of the aperture, surpassing largely the edge of the shell. In profile, the lip in the sutural zone is withdrawn and then projected forming a very marked sinus. Inner lip swelled forming a notable columelar callus.
Size: The specimens obtained in the Canary Islands (Tenerife, Gran Canada and Fuerteventura) had from 2 to 4 whorls.
Soft parts: The study of S. bonifaceae was done with specimens kept in fixative fluids, therefore we have not photos of living animals nor description of colour patterns were obtained. The preserved animals presented a uniform whitish coloration in the cephalic zone, and only big black eyes stood out. The gonad-visceral zone presents the same colour as the cephalic area, although some individuals were reddish brown. Operculum very thin, yellowish and transparent.

It was known from the Western Mediterranean and Sicilian Chanel, and from Bay of Biscay to the Ibero-Moroccan Gulf. Here recorded for the first in the Canary Islands. Sabinella bonifaciae was found living on the sea urchin Cidaris cidaris (L., 1758). The specimens observed in the Canary Islands were found crawling freely on the sea urchin, indicating that they are sporadic parasite, capable of freeing themselves from the host. S. bonifaciae is parasite of C. cidaris jointly with the eulimid Nanobalcis nana. In specimens of C. cidaris from Tenerife the latter was much more abundant than the former.

According to BOUCHET AND WAR£N (1986) the females of this species are larger than the males and are permanently adhered to the host, meanwhile the males may crawl freely. This species has tentacles smooth, wide and short, with eyes located at the base of each one. The foot is well developed and functional and, after comparing the shell's size of the veliger larva with the postlarval specimens, concluded that the size difference indicated a planktotrophic development.