The sea-snail produces a liquid from in the middle of its throat, where there is a white vein containing a very scanty fluid of a dark rose color. This liquid is the source of a purple dye that is much sought after for coloring clothes. Sea-snails hide for 30 days at the time of rising of the Dog-star, but gather in the Spring. It is said that if a ship has its sides covered in sea-snails it will be brought to a standstill by them, as happens with the echeneis.

If the sea-snail is cut with an iron blade, it produces purple tears, from which purple dye is made and used to dye clothes.