Ozius deplanatus

Adults average 57 mm (2.2 in) in size with a flattened oval-shaped carapace that is wide in the front with blunt lobed edges. This can be a rusty red to chocolate brown colour with light mottling. Underside may be a paler cream colour.^[3] The antennae are dark red to brown. Claws are large with a smooth texture.^[3] Fingers may be black or brown in colour.^[2] Walking legs are pale red with golden setae or hairs.^[2]

The black finger crab is a scavenger.^[6] It feeds on snails, half-crabs and hermit crabs. It is known to chip away at the shells of larger snails before grasping the animal with its mouth-parts. Smaller snails are crushed by the crab's large claws. It also feeds on limpets and chitons by using the tip of its claw to remove them from a rock.^[2]

It will spread its claws when started or threatened.^[2]