The depressed, imperforate, solid shell has a heliciform shape.

It is covered with a strong blackish cuticle, beneath which it is green.

The body whorl is large, flattened above, with incremental wrinkles and subobsolete spiral sulci.

[2] Lunella smaragda is an endemic species found both at the intertidal and low subtidal rocky shores and soft substrates (including seaweeds) of New Zealand.

[3][4] It is found around the North, South, and Stewart islands, on rocks between low and mid tide.