This snail is very similar to the other black top snails and they are often found together. This snail is solid, globe like with a blunt spire, flattened sides and an angular outline. The surface is smooth with indistinct spiral lines and is black or puplish black, sometimes grey. It may have a few yellowish white spots. The interior of the shell is a reddish colour and is iridescent.

Common especially in southern NZ. Upper to mid intertidal. Mainly under boulders on semi-exposed to sheltered rocky shores.

It feeds on the microalagal films wich cover the surfaces of rocks and on seaweed.

NZ Coastal Marine Invertebrates; Vol 1