Rugose land crab
Infra-order Brachyura, Family Gecarcinidea
Rugose land crab | Discoplax rotunda (Quoy and Gaimard, 1824)
A medium sized crab with a carapace up to 80 mm wide. Overall black, dark purple to purplish-brown coloring including legs. Paler to cream at claw tips. The carapace is not prominently inflated and has a distinct outer ridge extending back from outside of eyes. Outer surface of carapace with numerous scattered flattened to rounded granules extending down sides and out over legs and claws. Usually has two pale spots in middle rear of top of carapace although these may not always be present.
Found in thick vegetation on soils above shoreline and beyond spray zone. Digs shallow burrow and hides under vegetation debris. Very timid and has only been observed on the shore terrace near The Blowholes on Christmas Island however suitable habitat exists at other locations.
Read more about Christmas Island's rugose land crab in the book
"Crabs of Christmas Island" by Max Orchard