Volvulella acuminata
Habitat: it lives in the infralittoral zone, in a sandy and muddy habitat often near Posidonia.
Distribution: it can be found all over the Mediterranean. Common enough.
Notes: this species has got an unmistakable shell morphology easily recognizable from all other species of the Family Retusidae since, as unique exception, it has neither gastric plaques nor radula. Stretched and tapered in outline, apex sharp. On a stretch median part is cylindrical then it tapers in basal part which is roundish. Aperture narrow and stretched, widened in the lower part. Lip thin, columella presents a quite distinct fold. Surface smooth and bright, semitransparent, with some slight spiral lines only more evident in the lower part of last whorl.
Assignment of this species either to the genus Volvulella Newton, 1891 or to the genus Rhizorus Montfort, 1810 is not yet clear as well as whether these genera are synonyms. Average measures of adult specimens reach 2.5-3 mm in height.