Cystiscus is a taxonomic genus of minute sea snails, marine gastropod mollusks or micromollusks.

Shell minute to small, white, hyaline; spire immersed to low; lip thickened, smooth or weakly denticulate; external varix absent; siphonal notch absent; posterior notch absent; lacking collabral parietal callus ridge; columella multiplicate, with combined usually 2 to 8 plications plus parietal lirae, first plication usually strong and raised.

Lip slightly to distinctly thickened, flared posteriorly in some species, smooth on inside edge to weakly denticulate, lacking lirae, external varix absent.

Eocene of France and Alabama, upper Oligogene and Miocene of Western Atlantic, to Recent.

The shell of Persicula is usually patterned, often has a distinct external varix, and the spire is usually immersed.