A medium-sized chiton with an unusually smooth finish: the eight plates are glossy and nearly free of sculpture, and the girdle around them is bare and leathery rather than scaled or bristled. That combination makes it one of the easier chitons to name without a lens. Color is variable - green, olive, brown or reddish, often streaked or banded across the plates, with the pattern running lengthwise down the animal. Length reaches about 30 mm (1.2 in).
It lives on shallow rock, dead coral and reef flats from the tide line down to about 8 m (26 ft), sheltering by day under ledges and in crevices and emerging at night to graze. The diet is algal film scraped from hard surfaces, and each animal works a small home range, returning to the same spot before daylight. The species name records Erythraeum, the classical name for this sea; it was described from here, though the species is also known further along the East African coast. Like all chitons it can curl into a ball when detached, which protects the soft underside but leaves the animal helpless until it finds rock again - a pried-off chiton rarely survives, and there is no reason to lift one.
- smooth, glossy plates with little sculpture
- girdle bare and leathery, without scales or spines
- plates often streaked green, brown or reddish
