 44 species of crab and 9 species of amphipod were recorded there by the Percy Sladen Trust Expedition of 1916.492 species of marine mollusc have been recorded from the shallow waters of the Houtman Abrolhos.These are predominantly gastropods (346 species, 70%) and bivalves (124, 25%); the remaining 5% of species consist of cephalopods (14 species), chitons (5 species) and scaphopods (3 species).