Fossarina petterdi

Fossarina petterdi is a species of very small sea snail, a marine gastropod mollusc or micromollusk in the family Trochidae, the top snails.

Description
The shell grows to a length of 4 mm. The shell is narrowly umbilicated, faintly spirally striate, with hardly visible longitudinal striae. It is dark purplish black, with a few irregular white markings. The three whorls are convex. The body whorl is large and rounded. The umbilical region is white. The interior is greenish black, showing the external white markings. The thin, horny operculum is multispiral.

Distribution
This marine species is endemic to Australia and occurs off South Australia, Tasmania and Victoria