About Erronea onyx (Linnaeus, 1758)
Erronea onyx is a fairly common species of cowrie. On average, the shells of this species reach 32–38 millimetres (1.3–1.5 in) in length, with a recorded minimum shell size of 24 millimetres (0.94 in) and a maximum shell size of 57 millimetres (2.2 in). The dorsal surface of the Erronea onyx shell is smooth and shiny, and is generally golden brown, marked by alternating fuzzy longitudinal bands of translucent bluish and reddish coloring. This banded color pattern is the source of the species' Latin name onyx. The base and margins of the shell are dark brown or black, and the shell's teeth sometimes appear orange. Living individuals of this species have a thin, dark brown mantle that bears bluish papillae. This species is found in the Indian Ocean along the coasts of Aldabra, the Comores, Kenya, Madagascar, Mauritius, Mozambique, Réunion, the Seychelles, and Tanzania. It also occurs in the Pacific Ocean along the coasts of East China, Thailand, northern Australia, Indonesia, the Philippines, the Palau Islands, and the Solomon Islands. Erronea onyx inhabits tropical and subtropical regions, living in shallow subtidal water at depths ranging from 5 to 25 metres (16–82 ft). It occurs most commonly on muddy or sandy sea floors, and feeds on algae and coral polyps.
