A smooth cream shell with a few large dark blotches, out on the sand after dark.
A heavy, smooth-shelled crab with a carapace to about 15 cm across, glossy cream to pale orange and marked with a small number of large, round, well-separated dark red-brown blotches. The count varies with which of the marks on the claws and legs are included, which is where the seven-eleven name comes from; spotted reef crab is the other name in circulation. The shell carries no teeth, spines or sculpture along the margin: it is a plain dome, and the widely spaced round blotches separate it from the mosaic crab Zosimus aeneus and the heavy xanthids, whose markings are hard-edged and joined into a network across the whole shell. Carpilius convexus has the same build and size but is plain brick-red to orange-brown.
Nocturnal. By day it is wedged under rubble, coral slabs and debris, and after dark it walks out onto open sand and rubble. The claws are heavy and unequal and are used to break the shells of snails and hermit crabs, so broken shell accumulates around a shelter that is used regularly. It is slow, does not flee, and relies on the shell rather than on speed.
Recorded from the shallows to about 30 m, more often on the harder rubble margins of a muck site than out on fine silt.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
