Of the two main kinds of purple-yielding shellfish described by *Pliny (1) (HN 9. 125–41), purpura and pelagia (Greek πορφύρα) correspond to the Linnaean murex, murex and bucinum (κῆρυξ) to the smaller and less precious purpura haemostoma. In antiquity the purple of *Tyre always retained its primacy, but purple dyeing was practised also in the Greek cities of Asia, the Greek mainland and islands, S. Italy, and N. Africa. After being gathered or caught in baskets and killed suddenly to preserve the secretion, the molluscs were either opened (esp. the larger) or crushed. The mass was then left in salt for three days, extracted with water, and slowly inspissated to one-sixteenth of its original volume. Impurities were removed during this process, and the liquid was then tested with flocks of wool until the colour was right. Many shades within the violet–scarlet range, and even a bluish green, could be obtained by mixing the dyes from different species and by intercepting the photochemical reaction which gives the secretion its colour. (‘Twice-dyed’ (δίβαφος) Tyrian purple resulted from consecutive steeping in pelagium and bucinum.