2 smooth whorls of tectiform shape with large nucleus. Sculpture of 14 or 15 weak axial ribs, about their own width apart on spire but more distant on body-whorl. These are crossed by numerous close spiral threads, well marked on shoulder but becoming obsolete on sides of whorls. Aperture elongate, not notched below; outer lip slightly sinuous. Columella with four distant folds, anterior one weak, others strong.

Height, 12.5 mm.; diameter, 6 mm.

Holotype in collection of N.Z. Geological Survey.

P. incisula is easily distinguished from others of the genus by its small size, rather plump outline and spiral sculpture of close threads well marked only on the shoulder.