Oval, asymmetrical and up to 30 irregular ribs. The shell can often be eroded or encrsted with algae or other animals. externally the shell is grey to light grey brown and the grooves beteen the ribs are often dark brown. Internally the shell is blue on the spatula (where the siphon comes out) and yellowish tan, mottled with dark brown or grey.

Found at and above mid tide level.

Grazes on algae on the rocks.

It is an air-breathing pulmonate who returns to a home scar at low tide. It lays a yellowish semi-circular egg mass on the rocks.

NZ Coastal Marine Invertebrates; Vol 1