The genus Crisilla was erected by MONTEROSATO (1917) to separate from Cingula all the numerous Mediterranean and Macaronesian species morphologically similar to C. semistriata. Subse-quently, the treatment of this supraspecific taxon has varied over time. VERDUIN (1984) did not consider Crisilla with generic value and included its species within the genus Cingula. It was treated as subgenus of Alvania by PONDER (1985), but it was later given genus rank by BOUCHET & WAREN (1993) based on the morphological homogeneity of shells among its species. They included in Crisilla some species whose shell is similar in shape to the type species (C. semistriata), which is usually semitransparent with brownish square blotches. One unusual feature shared by these species (according to BOUCHET & WAREN, 1993) is the pair of subsutural furrows, also present in Alvania zylensis Gofas & Waren, 1982, species they believe that may belong to this group. Although this species meets several of the characters assigned to the genus Crisilla, due to the characteristic zig-zag pattern of the sculpture of its protoconch we think it should be more related to species of Benthonellania or to one of the lineages of Alvania. TEMPLADO & ROLAN (1994) provided a table indicating the distinguishing characteristics of the shell and soft parts to differentiate the genus Crisilla from Alvania, Cingula, Setia and Obtusella Cossmann, 1921 and described some new species from Cape Verde Islands. Crisilla is now considered as a valid separated genus in the current checklists and databases (CLEMAM, 2017; MolluscaBase, 2018) and up to 30 species are assigned to it, including C. gagliniae (Amati, 1985) and C. maculata (Monterosato, 1869) as recently suggested by APPOLLONI ET AL. (2018), all from the Eastern Atlantic and Mediterranean, except Crisilla angustostriata van der Linden, 2005 from the Indian Ocean (see Table I). All Crisilla species except C. semistriata and C. transitoria Gofas, 1999 have paucispiral protoconch, which is indicative of a non-planktotrophic larval development. Nine species of the genus are known in the Mediterranean (two of them also present in the European Atlantic), one is an Atlantic bathyal species, one is present in Azores Islands, nine in Madeira and/or Canary Islands, three are distributed along the continental coasts of West Africa, six were described from the Cape Verde Islands (TEMPLADO & ROLAN, 1994), and one from Mozambique, Indian Ocean (VAN DER LINDEN, 2005).

KEY FEATURES:
We consider a priori the following characters to include species in the genus Crisilla:
Size: between 1 and 3 mm.
Shell shape: pupoid; width somewhat more than half of its height; whorls moderately flat to convex, with a shallow suture slightly canaliculated and with one or a pair of subsutural furrows. Aperture large, ovate-rounded, shorter than half of shell height, without a clear labial rib on outer lip with the exception of a few species: e.g. C. transitoria, C. cristallinula, and C. semistriata which may occasionally bear a single or double varix on the last whorl, internally smooth or with a weak denticulation.
Sculpture: spirally sculptured, without or with incipient axial ribs. Spiral sculpture mainly close to the suture and the base, consisting of narrow spiral furrows demarcating broad, flat spiral cords. One distinctive feature is the pair of subsutural furrows delimiting a well-marked interspace. Microsculpture of dense growth lines without spiral elements.
Colour: shell usually translucent with a pale yellowish hue, often ornamented with spiral rows of red-brown square blotches. Protoconch: multispiral or paucispiral, usually with very weak spiral elements and minute granules more or less arranged into blurry spiral lines.