Page:Natural History, Mollusca.djvu/48

36 benefits of the Mollusca are to be estimated: they are useful also in the arts. The pearl, that splendid auxiliary to costume in all ages, glittering on the tiara of the Assyrian monarchs and on the diadem of our own sovereign, is a production of this class of animals, This, it is true, has no merit beyond its beauty, but the substance called mother-of-pearl is, as is well known, much used in the arts.



It consists of the interior layers of many species of shells, principally Bivalves; but some among the Univalves have an interior brilliantly nacreous. The Top-shells (Trochus), several species of which