The Retusidae are a family of small infaunal species possessing an external shell that is typically white and cylindrical in shape. The posterior end of the shell is truncate with the protoconch usually sunken.
There is a long aperture that widens anteriorly and a small operculum is present in some species of the genus Retusa but it does not completely fill the aperture. The surface of the shell may be smooth, or sculptured axially, or spirally, or both. The head shield is very shallowly bilobed anteriorly, and developed into two distinct lobes posteriorly.
Eye spots, though present on the head shield towards the base of the posterior lobes, can be difficult to discern. The foot is broad but short and never longer than the shell and does not develop parapodia.
The gill is not visible externally. They are very selective feeders and depending upon species consume foraminiferans, diatoms and small molluscs. They are preyed upon by the aglajid sea slugs.