Retusa mammillata
Habitat: it lives in the infralittoral zone in a sandy habitat.
Distribution: it can be found all over the Mediterranean. It is one of the most common species of its genus.
Notes: shell cylindrical in aspect, stretched, with same width all along outline made exception for a slight narrowing in medium-low part of spiral. Apex, mamilliform, coming out from spiral that, on last whorl, makes a shoulder at a right angle. Nevertheless there are found specimens with whorls of spiral protuberant assuming an aspect more or less turriculate and others with spiral either almost deepened or not much protuberant. External lip runs parallel and near columellar border all along its height. In the lower part aperture is not much large with columella arched.
Sculpture presents some slight longitudinal striae in apical zone and, all over surface, it presents some fine spiral striae visible under strong amplification. Its most similar one is R. truncatula that however is larger in sizes, it has an evident narrowing in upper half of whorl, its lower part is more enlarged, its protoconch is almost never protuberant and it has a different axial sculpture. Average measures of adult specimens reach 2.5 mm in height.