of-pearl
of commerce. Although the pearls which it yields are among the largest
and finest in the world, this mollusk is sought more particularly for
the shell, the value of which from season to season averages three or
four times as much as that of the pearls. Ordinarily this shell is
uniformly white over the entire inner surface, and is commonly known
locally as "silver lip"; but some "golden-edged" shell occurs on the
muddy grounds in narrow passages between the islands on the northwest
coast.
While
this species is gregarious, it is not located in densely covered beds,
but is scattered in patches over the reefs. Some of these are miles in
length and contain scores of tons, but usually they are very much
smaller. The oysters occur principally on rocky bottom, and also on
clay and sand when well covered with seaweeds, but are rarely found on
muddy ground. They are most numerous in the channels where the current
is strong. The small oysters are generally loosely attached by the
byssus to rock, gravel or other shells ; while the mature ones lie
loosely on the bottom or slightly turned in the sand.
The second species of the Australian pearl-oysters, Margaritifera margaritifera, is
smaller, rarely exceeding eight inches in diameter and a weight of two
pounds. The distinguishing characteristic is the black edge bordering
the inner surface of the shell, whence it acquired the local
designation "black lip." This variety is not rare in Queensland, and in
Western Australia its range extends as far as Champion Bay in Lat. 29 °
S. However, the catch is small compared with that of the Margaritifera maxima, amounting
to only two or three per cent, in Queensland. In 1905, the export of
"silver lip" and "golden-edged" from Thursday Island was 527 tons, and
of "black lip" only 11 tons; in 1904, these figures were 778 and 7
respectively. In Western Australia the percentage of yield is much
larger than this.
The third species, Margaritifera carcharium, is
confined almost entirely to the limits of Sharks Bay, on the extreme
western coast of Australia. At maturity it is the smallest of the
three, averaging three or four inches in diameter, and about equals in
size the Lingah pearl-oyster of the Persian Gulf. The percentage of
pearls therefrom is relatively greater than from the larger variety ;
but, owing to its small size and lack of thickness, the shell is of
little commercial value. The value of the output in recent years has
approximated two or three thousand pounds sterling, which is very much
less than formerly, the value of the shell having greatly decreased
since the introduction of the Mississippi shell in button manufacture.
The
pearl fishery on the coast of Australia originated about 1861. It
appears that an American sailor named Tays was the pioneer in the
business; and on his death by drowning, the business was conducted
