These tiny crabs measure about 2 cm across and have a squarish body.

Mottled crabs come in a wide range of colours, but are usually black, brown or greenish white with markings of orange, brown or black. Their striking patterns mean mottled crabs are also known as marble crabs or batik crabs.

Mottled crabs aren’t very common on Christmas Island, but can sometimes be found under leaf litter and rocks above beaches.