The name given to the long, delicate, shining fibres by which some of the bivalve shells attach themselves to submarine bodies. It is sometimes coarse and strong, as in the common mussel (mytilm edulis), or silky, as in the great p inna of the Mediterranean. According to De Blainville, it is not a secretion spun from a glandular organ, but a bundle of muscular fibres, which, though dried and apparently lifeless externally, are actively contractile at their origin near the foot; there seems to be a regular gradation from the ordinary foot to a true byssus. Along the Mediterranean the silky byssus of the pinna is woven into various articles, such as gloves and stockings, more curious than useful. II. The byssus of the ancients (Gr. ; Heb. hutz) has been the subject of many learned disquisitions, some critical authorities contending that it was cotton, and others that it was linen. It is not unlikely that the word was applied, in various connections and at various times, to both cotton and linen textiles. The mummy cloth of the Egyptians, which Herodotus designates as byssus, has been proved by microscopic examinations to have been linen.