[2] It may grow up to 4 centimetres or 1.6 inches long (carapace length).

[1] The name "masked crab" derives from the patterns on the carapace which resemble a human face (a case of pareidolia), in a similar manner to heikegani.

[4] C. cassivelaunus lives buried in sandy substrates, where it feeds on the infaunal invertebrates such as polychaete worms and bivalve molluscs.

[1] It uses its two antennae to form a breathing tube that allows oxygenated water down into the substrate.

[5][6] The chelipeds of males are much longer than the body, while those of females are only about as long as the carapace.