Body relatively broad and somewhat flattened so as to be oval in cross section. Paired fins run from behind the head to the tip of the body, but do not join. Arms are short and possess 4 rows of suckers while tentacular clubs possess 5-6 suckers in transverse rows. Dorsal margin of mantle with blunt lobe. Individuals are capable of very rapid colour change, especially when threatened; the animal may also take the colour or patterning of its background. Mantle reaching lengths up to 45 cm and weight up to 4 kg.