Diloma aridum is a species of small sea snail, a marine gastropod mollusc in the family Trochidae.

[1] The height of the shell attains 19 mm, its diameter 17 mm.

It is a purplish-black marine snail with pale yellow flecks in appearance.

[2] This marine species is endemic to Chatham Islands, New Zealand and Auckland Islands and occurs on sheltered mid-tidal rocks.

This Trochidae-related article is a stub.