Scyphoniscus magnus Chilton, 1909
New Zealand distribution: subantarctic islands (Auckland and Campbell Islands), on sea shore about high-water mark (Chilton, 1909). Body length 7-10 mm, dorsal surface with small, irregular tubercles.
Can be confused with Scyphoniscus waitatensis, which differs in distribution within New Zealand (North and South Island) and is much smaller (S. waitatensis males 3.5 mm, females 4.5 mm).
Can also be confused with juveniles of Deto, from which it differs in the shape of uropods (in Deto the rami of the uropods are similar in size, in Scyphoniscus the exopod is larger and more stout than endopod).