Pinna muricata Linnaeus, 1758
30-116 mm. —> Very elongated triangular shape, nearly transparent. Extremely fragile, shell rarely found intact. Each valve has a lengthwise seam down the middle of it A few-scales near the wider end. Juveniles are all white. Mature specimens may show irregular muddy-looking areas. (116 mm) Distribution: Moderately common, all regions.
Notes: Sometimes one finds broken bits of a much heavier similar shell. These may be subfossil remains of a species no longer found in the northern part of the Red Sea, Pinna bicolor Linnaeus, 1758.

Shell length to 300 mm; usually thin, attenuately triangular in shape; posterior margin usually sharply truncate, moderately inflated. Sculpture: 12-26 radiating spined ribs, usually with finer, non spine-bearing ribs between them; spines usually upright and open posteriorly, sometimes abraded; internally the medial sulcus is very narrow and the ventral nacreous layer truncate. Colour: light horn, with dark brown blotches posteriorly. Habitat: littoral sand. Distribution: New South Wales, Queensland to north Western Australia.