Although this shell, and several other species which nearly resemble
it, are known by the trivial name of _Mussel_, the only resemblance
between them consists in their outward appearance, the animals which
inhabit the shells being very distinct, both in organization and in
habits. The Mussels, as we have already said, have very little power
of moving from place to place, while, on the other hand, the Anodonta
is at times far from being a sluggish animal, and, for the purpose of
shifting its position, it avails itself of a very strong and broad
muscular foot. The shell of the Anodonta is sometimes found to contain
pearls, a circumstance which frequently occurs in all shells which are
lined with mother-of-pearl.
Some of the Scotch rivers have produced numerous specimens of pearl,
very large and beautiful, and which used to bear an extremely high
price.
A paper in the Philosophical Transactions for 1693, mentions the
collection of pearls from this shell, in the river Omagh, County
Tyrone, in Ireland. “The poor people,” he says, “in the Summer months,
go into the water, and some with their toes, some with wooden tongs,
and some by putting a sharpened stick into the opening of the shell,
take them up; and, although, by a common estimate, not above one shell
in a hundred may have a pearl, and of these pearls not above one in
a hundred be tolerably clear, yet a vast number of fair merchantable
pearls, and too good for the apothecary, are offered for sale by those
people every Summer assizes. Some gentlemen of the country make good
advantage thereof, and myself, whilst there, saw one pearl bought for
50_l._ that weighed thirty-six carats, and was valued at 40_l._ A
miller took out a pearl, which he sold for 4_l._ 10_s._ to a man that
sold it for 10_l._, who sold it to the late Lady Glenanly for 30_l._,
with whom I saw it in a necklace; she refused 80_l._ for it from the
late Dutchess of Ormond.”
[Illustration: _Isocardia cor. Anodonta Cygnæa._]