Chrysallida obtusa: General description (after 1810 shells from 38 localities). — The shape of the shell is very variable, from compact conical (B/b 2.1) to slender, nearly cylindrical (L/B 2.9 and B/b 1.3) with a blunt top. The protoconch is of the type B. There are four or five flat to slightly convex teleoconch whorls, the last one relatively high. The suture is generally narrow and deep (although specimens with a wider suture also occur), sometimes (nearly) horizontal, sometimes oblique. The ribs are broader than or equal to the interspaces, straight and vertical, occasionally somewhat inclined to the right or the left. They end abruptly at the last spiral, just above the aperture. In a small percentage of the shells (very rarely from Atlantic origin) the ribs continue, decreasing or not, to the base . In some shells the ribs may be close together or may be slightly curved or flexuous as well. The spiral pattern is not so variable; the initial whorls have one spiral, just above the abapical suture, the last whorl has two spirals on the periphery, the lower one is a real spiral when the ribs continue to the base, but mostly, when the ribs end abruptly, it is more a border of interstices and ribs. The aperture is oval-sperical to narrow egg-shaped or rhomboid. The tooth is generally directly visible, often only after turning the shell to the left. There may be an umbilicus, an umbilical chink or no umbilicus at all.
Length 1.7-3.2 mm, LW 29-67%, A 26-41%, L/B 1.8-2.9, B/b 1.3-2.1 (based on 82 shells).

AS Chrysallida obtusa
Habitat: it lives in the infralittoral and circalittoral zones.
Distribution: it is found all over the Mediterranean. Common enough in its several forms.
Notes: this species is to be considered the most common one of its genus and it is really variable in its outline and sculpture. Shell stretched, conic, whorls flat-sided and suture broad. Sculpture made by axial ribs quite strong, either straight or a little bit undulated, more or less as wide as interspaces that are usually interrupted at the base. A very important characteristic for its determination is the presence of an evident spiral cord below-suture all over the whorls, made exception for the last one where there are present two cords one of which at the periphery of axial ribs. Aperture ovoidal in form with one tooth quite visible generally. Umbilicus more or less evident. Protoconch type B. These characteristics are quite evident in juvenile specimens too. C. farolita, set up by Nordsieck, 1972, on imaged shells col¬lected at Ibiza (Spain), is considered as a synonym of this species. Perhaps this species is better known under synonym C. interstincta (Adams J., 1797). Average measures of adult specimens are around 2.5-3 mm in height.