The carapace (shell) of this small crab is slightly longer than it is wide and grows to a width of in males and in females. The rostrum (the part of the carapace in front of the eyes) has two flattened projections which spread apart. The margin of the carapace has a pair of large teeth on either side of the rostrum and another, more flattened pair, slightly further back. The carapace is scattered with small tubercles. The legs are long and bear spines which may help the crab cling onto the kelp. The colour of this crab varies, usually being brown, red or yellow, but sometimes being orange, pink, white or blue. The chelae (claws) have blue extremities, with red, orange or white tips, and the walking legs often have pale bands.
