Cythara paucicostata is a species of sea snail, a marine gastropod mollusk in the family Mangeliidae.
This species is considered a nomen dubium.
The length of the shell attains 7 mm, its diameter 3 mm.
(Original description) The wholly white shell has an oblong, ovate shape. The spire is rather short, turreted and acute. The whorls are angulated at the sutures, longitudinally ribbed. There are 7 ribs, very prominent, compressed, running into the sutures. The interstices are concave, finely, regularly and closely striate transversely. The sutures are deep.[1]
This marine species occurs off Tahiti and Polynesia.