It can grow to a length of 20 cm (7.9 in),[2] although most specimens only reach half that size.

[2] N. antiqua is found in the Northeast Atlantic along cold-temperate European coasts, ranging from the low water mark[4] to a depth of 1,200 m (3,900 ft).

[3] N. antiqua is primarily a scavenger, although it has been recorded attacking and eating some living polychaete species.

[4] Unlike several of its more predatory relatives, experiments have shown that even hungry N. antiqua are not attracted to living undamaged mussels.

[4] N. antiqua contains tetramethylammonium salts (most likely the chloride) in its tissues, and has been the source of non-lethal human poisoning.