Then the common edible mussel frequently contains Pearls, which, however, are almost invariably small, and comparatively valueless. It is mentioned by Pliny that Julius Cæsar obtained in Britain a sufficient number of Pearls to cover a breastplate, which he dedicated to Venus, and hung in her temple. It is evident from Pliny's account that the Pearls in question were small and comparatively valueless, and it has been shrewdly suggested that Cæsar only presented them to the goddess because the Roman ladies would not have worn them.
These Pearls were in all probability obtained from the common edible mussel which grows so abundantly on our coasts, and not, as has been generally thought, from the river Pearl-mussel, which really produces Pearls of considerable value. The celebrated pearl-fishers of the Conway employ the edible mussel, and sell the Pearls at a certain price per ounce.
The scientific name of the river Pearl-shell is Unio margaritiferus, which is found in best condition in rapid mountain streams. It is plentiful in many of the Irish rivers, from which Pearls of considerable value have been procured. One of these Pearls, seen by Sir R. Redding set in a necklace, was purchased for thirty pounds by the owner, who had refused nearly three times the sum for it.
Perhaps the most celebrated Pearl-mussel is that of the Chinese, Dipsas plicatus. This species attains a considerable size, a specimen in my possession being seven inches in length and five in width.
PEARL OYSTER.
"And the twelve gates were twelve pearls."—Rev. xxi. 21.
The Chinese make a singular use of this mussel. They string a number of globular pellets, and introduce them between the valves of the mussel, so that in course of time the creature deposits a coating of pearly substance upon them, and forms a very good imitation of real Pearls. They also stamp little images, popularly called josses, out of metal, and force the animal to cover them with nacre in a similar manner. Six such josses are in my specimen. Frequently, however, these incorrigible imitators actually counterfeit the sham pearls, merely taking the josses and pellets, laying them in shells from which the animal has been removed, and washing them with a solution which, when dry, looks so like nacre that it cannot be distinguished from that substance without much difficulty.
The best Pearls are those which are procured from the well-known Pearl Oyster (Meleagrina margaritifera), which is found in several parts of the world, and which constitutes the principal source of wealth to the localities where it most abounds.